docs: warn about flutter snap package

[2bndy5]

resolves #498

Changes

This replaces a footnote (about avoiding the flutter snap package) with an admonition and notes that app stores (at least on debian-based Linux distros) offer flutter SDK as a snap package.

[2bndy5]

I see you've pushed some changes. The only one that I'd object to is using the same hyperlink target twice without taking advantage of Markdown's substitution mechanism.

But it's not my call to make...

[temeddix]

I see your point. I was trying to match the formatting with that of other pages, but I think your method can also work.

I'll restore the link as per your suggestion :)

[2bndy5]

I'm pretty good with mkdocs and Github Actions.

Using ReadTheDocs can allow a way preview docs changes in a PR without building the branch locally (see RTD docs for more detail)

I would also limit the other CI triggers to only run the workflow on relavent changes (see gitub docs for more detail). For example, it wouldn't make sense to run unit tests on changes that only affect the docs 😉 . Here, I think the test-app and example-app CI ran because of the addition to gitignore.

[temeddix]

Currently, *.md files are excluded from the app build tests, but perhaps the .gitignore file can also be added to the list.

Any RTD-related PR is also welcome if it actually improves the workflow.

[2bndy5]

Any RTD-related PR is also welcome

An admin for cunarist would have to import this repo into a RTD account (using Github credentials to sign in) and enable PR builds in the RTD project's settings. Afterward, it would be as simple as adding a .readthedocs.yml to tell RTD how to build the mkdocs project located in documentation/. No additional CI workflow needed.