docs: release notes for 3.3

docs/docs/reference/release-notes/v3.3/index.md

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+---
+date: "2021-04-13"
+version: "3.3.0"
+---
+
+# [v3.3](https://github.com/gatsbyjs/gatsby/compare/[email protected]@3.3.0) (April 2021 #1)
+
+Welcome to `[email protected]` release (April 2021 #1)
+
+Key highlights of this release:
+
+- [Performance optimizations](#performance-optimizations) - faster JS bundling, lower peak memory usage
+- [Upgrade to the latest `sharp`](#upgrade-to-the-latest-sharp) - built-in image optimizations; and now works on M1 Macs
+- [Upgrade to the latest `remark`](#upgrade-to-the-latest-remark) - more consistency in Markdown rendering
+
+Also check out [notable bugfixes](#notable-bugfixes--improvements).
+
+**Bleeding Edge:** Want to try new features as soon as possible? Install `gatsby@next` and let us know
+if you have any [issues](https://github.com/gatsbyjs/gatsby/issues).
+
+[Previous release notes](/docs/reference/release-notes/v3.1)
+
+[Full changelog](https://github.com/gatsbyjs/gatsby/compare/[email protected]@3.3.0)
+
+---
+
+## Performance optimizations
+
+### Faster JS bundling
+
+This release adds memoization of babel loader options. It significantly reduces the overhead in JS compilation step.
+With our sample site we saw a speed-up in JS bundling up to 30-40%
+
+Note: this improvement only affects JS bundling, so if you use other heavy transformations (CSS-in-JS, Mdx, etc),
+you will likely see modest improvements.
+
+[Original PR](https://github.com/gatsbyjs/gatsby/pull/28738/)
+
+### Lower peak memory usage
+
+This release restricts concurrency of html-file generation which can greatly reduce memory and disk pressure
+and decrease spikes in memory usage — especially for sites with many 100s+ pages and large page-data.json files. With our example site we saw a decrease in peak memory usage from ~3.5 GB to ~1.7 GB (without negative effects to build time).
+
+[Original PR](https://github.com/gatsbyjs/gatsby/pull/30793)
+
+## Upgrade to the latest `remark`
+
+Remark has had a significant [major upgrade](https://github.com/remarkjs/remark/releases/tag/13.0.0)
+recently (version 13) and changed the underlying parser. The ecosystem has almost [caught up](https://github.com/remarkjs/remark/blob/main/doc/plugins.md#list-of-plugins)
+since then, so we've decided to release new major versions of all our `remark` plugins.
+
+The following plugins are now fully compatible with `remark@13`:
+
+- **[email protected]**
+- [email protected]
+- [email protected]
+- [email protected]
+- [email protected]
+- [email protected]
+- [email protected]
+- [email protected]
+- [email protected]
+- [email protected]
+- [email protected]
+- [email protected]
+
+We've tried to make the migration effortless and non-breaking (just update the dependencies)
+but there are subtle differences in HTML output caused by the new remark parser.
+We've identified and listed the most common differences [in this discussion](https://github.com/gatsbyjs/gatsby/discussions/30385)
+(if you spot other notable changes - please comment there!)
+
+Also check out [remark changelog](https://github.com/remarkjs/remark/releases/tag/13.0.0), specifically the section: "Changes to output / the tree".
+
+### Incompatible plugin: gatsby-remark-custom-blocks
+
+The only plugin provided by Gatsby that is not compatible yet with `remark@13` is
+[`gatsby-remark-custom-blocks`](https://www.gatsbyjs.com/plugins/gatsby-remark-custom-blocks/).
+This plugin relies on the upstream remark plugin `remark-custom-blocks` which is itself not compatible with
+`remark@13` yet.
+
+The work on updating it is [in progress](https://github.com/zestedesavoir/zmarkdown/issues/416)
+though, and as soon as it is finished we will publish the new major version for our plugin as well.
+
+In the meantime if you use this plugin you can just wait when it's ready or modify your markdown
+and switch to another syntax. Remark authors [suggest](https://github.com/remarkjs/remark/blob/main/doc/plugins.md#list-of-plugins)
+using [`remark-directive`](https://github.com/remarkjs/remark-directive) as an alternative.
+Use [`to-gatsby-remark-plugin`](https://www.npmjs.com/package/to-gatsby-remark-plugin) package to convert it to Gatsby remark plugin.
+
+- [Umbrella discussion](https://github.com/gatsbyjs/gatsby/discussions/30385)
+- [Original PR](https://github.com/gatsbyjs/gatsby/pull/29678)
+
+---
+
+## Upgrade to the latest `sharp`
+
+Check out [Sharp changelog](https://github.com/lovell/sharp/blob/ed5d753b89e5649b1586de04ffef6ec903942a64/docs/changelog.md#v028---bijou)
+for a full list of changes.
+
+The most important highlights of the new release:
+
+- Smaller install size
+- Supports Mac M1: now uses prebuilt libvips binaries for M1 Macs
+- Includes buil-in image optimization (unlocks future perf improvements in Gatsby)
+
+[Original PR](https://github.com/gatsbyjs/gatsby/pull/30541)
+
+## Notable bugfixes & improvements
+
+- Fixed invalid query results in cached builds [PR #30594](https://github.com/gatsbyjs/gatsby/pull/30594)
+- Schema customization: merge fields of interfaces defined by multiple plugins [PR #30501](https://github.com/gatsbyjs/gatsby/pull/30501)
+- Fix for IE11: add dom collections to polyfills [PR #30483](https://github.com/gatsbyjs/gatsby/pull/30483)
+
+## Contributors
+
+TODO after backporting all fixes