Validate that code snippets in docs are at least "analyzer clean"

[matanlurey]

I believe (?) @chalin and others had a tool for this at one point.

Basically I'd have love to catch that:

const ClassProvider(Foo, ConcreteFoo);

... was an incorrect example (missing the useClass: named parameter).

Might not be worth doing, though.

[chalin]

If this is related to #992, I was going to suggest that we integrate that page into site-webdev since we have there the necessary infrastructure allowing code excerpts to be analyzed and/or tested.

Actually, as @kwalrath mentioned already, it might be a good idea to have an Effective Angular section under site-webdev, similar to the Effective Dart section under dartlang.org.

FYI, regarding tooling, the Flutter site has some tooling to extract code excerpts and then analyze them. Under site-webdev, we use the usual tools to analyzer and test code. Instead we have a code excerpt extractor that scans the code, picks out fragments, and embeds the fragments into the docs. The approaches are complementary.

[matanlurey]

As mentioned elsewhere, I'd really like this to be in our own repository - and to figure out a syncing strategy. This stuff changes often, and the cognitive load of needing to land the CL separate to updating the best practices doesn't seem worth it.

[alorenzen]

Also, if it is in our own repository, we can reference it easier internally as well.