doc: Simplify the "minimum required versions" page using MyST customized URL schemes

[seisman]

Description of proposed changes

MyST supports customized URLs.

References:

• https://myst-parser.readthedocs.io/en/latest/syntax/cross-referencing.html#customising-external-url-resolution
• https://myst-parser.readthedocs.io/en/latest/configuration.html#frontmatter-local-configuration

Preview: https://pygmt-dev--3383.org.readthedocs.build/en/3383/minversions.html

This page doesn't change but the markdown file is much shorter!

[yvonnefroehlich]

Hm. Based on how I understand the documentation so far and being consistent with url_schemes:, using "URL" seem to be better, here. If we use "URI" I feel it can make sense to introduce this shortcut.

Suggested change

	# Customized URI schemes that are converted to external links
	# Customized URL schemes that are converted to external links

[michaelgrund]

For me it seems URI is still the right term here since an URL is already a link (a location) while an URI is just the identifier that is then converted to an URL.

[seisman]

The MyST documentation uses URI: https://myst-parser.readthedocs.io/en/latest/configuration.html

For the difference between URI and URL, see https://www.godaddy.com/resources/ae/skills/uri-vs-url.

I agree with @michaelgrund that URI is the right term.

[yvonnefroehlich]

Hm, looks like the MyST documentation is not 100 % consistent here 🙃:

at https://myst-parser.readthedocs.io/en/latest/syntax/cross-referencing.html#customising-external-url-resolution

To specify a custom list of URL schemes, you can set the myst_url_schemes configuration option. By default this is set to ["http", "https", "ftp", "mailto"].

but at https://myst-parser.readthedocs.io/en/latest/configuration.html

myst_url_schemes | URI schemes that are converted to external links (default: {'http': None, 'https': None, 'mailto': None, 'ftp': None})

[seisman]

Anyway, it's just one comment line and it doesn't hurt if it's correct or not.

[yvonnefroehlich]

Reading https://www.godaddy.com/resources/ae/skills/uri-vs-url

URIs can be further divided into two categories: URLs and URNs. [...]
The key difference is: all URLs are URIs, but not all URIs are URLs.

So, let's keep URIs here.