Move and lint ECMA-335 Augments spec

[jnm2]

Followup from dotnet/csharplang#2608 (comment):

Yes, I think it would be fine to start a ECMA-335 Augments doc where we will collect additions to ECMA-335 we would like to do, but do not have a good way to do currently. We have number of those.

Actually, we have a doc like already: https://github.com/dotnet/runtime/blob/master/src/libraries/System.Reflection.Metadata/specs/Ecma-335-Issues.md . We should build on top of it. Rename it ...Augments, and maybe move this whole directory to a more discoverable place, e.g. docs\design\specs.

Once this PR is merged, I will start a PR to add a new section. The new section will need to be considered an official runtime specification and vetted by the runtime team. (See dotnet/roslyn#43281 (comment).)

There are 11 remaining markdownlint warnings. Any or all of the linting commits can be dropped, just ask.

/cc @jkotas

[jkotas]

I would move all docs from https://github.com/dotnet/runtime/blob/master/src/libraries/System.Reflection.Metadata/specs/ to this directory

[jkotas]

Add a link to this doc from https://github.com/dotnet/runtime/blob/master/docs/project/dotnet-standards.md#ecma-335---cli ?

[jnm2]

@jkotas Thanks for the help. All addressed!

[jkotas]

Thank you!