feat(npm): add support for resolving "import" conditions to ESM (#400)

* feat(project): emit .mjs files for ESM bundle

* chore: add changeset

* fix: update references in exports to use .mjs

* fix: update entry for size-limit

* ci: update type-check job

* refactor: emit package.json with "type" instead of .mjs files

* chore: update size-limit entrypoint

* chore: update changeset

* chore: use explicit .mjs extension

* chore: add optional dependencies for ci

* chore: update size-limit entry point

Author: joshblack

.changeset/clean-kangaroos-repeat.md

@@ -0,0 +1,5 @@
+---
+'@primer/behaviors': minor
+---
+
+Update the output of the package to correctly map "import" conditions to ESM

.github/workflows/ci.yml

@@ -47,3 +47,7 @@ jobs:
         run: npm ci
       - name: Check TypeScript types
         run: npm run type-check
+      - name: Build package types
+        run: npm run build
+      - name: Check published TypeScript types
+        run: npx @arethetypeswrong/cli --pack .