Add rust-analyzer usage to documentation

[yagehu]

This commit adds the instructions for setting up rust-analyzer support
to the main documentation landing page. The instructions were originally
given in #505.

[UebelAndre]

Thanks for the PR! Before digging into this, just wanted to get some thoughts on whether or not we should use the doc attribute from the rust_analyzer_aspect rule. This would closer tie the documentation to the implementing code. I definitely think rust_analyzer should be called out on the first page but am wondering if the bulk of the docs should live with the rules

rules_rust/rust/private/rust_analyzer.bzl

Lines 104 to 110 in 881d93a

	rust_analyzer_aspect = aspect(
	attr_aspects = ["deps", "proc_macro_deps"],
	implementation = _rust_analyzer_aspect_impl,
	toolchains = [str(Label("//rust:toolchain"))],
	incompatible_use_toolchain_transition = True,
	doc = "Annotates rust rules with RustAnalyzerInfo later used to build a rust-project.json",
	)

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[UebelAndre]

Hey, sorry about the commit that was added to this PR. I'd love to see documentation for rust analyzer go in but you'll have to drop that commit first 😅

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[yagehu]

Hey, sorry about the commit that was added to this PR. I'd love to see documentation for rust analyzer go in but you'll have to drop that commit first sweat_smile

Dropped the commit. Sorry for the delay.

[UebelAndre]

Hey @yagehu, I ended up using your changes here in #711 for the rust-analyzer section. I wanted to thank you again and apologize for "stealing your thunder" 😅

Gonna close this for now since virtually all the changes here are already merged