Include .rbi shims in yard docs

[dduugg]

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Per https://github.com/dduugg/yard-sorbet/blob/main/README.md we can merge the RBI sigs with source code documentation. The add'l time is ~negligible (27s now, 24s before). This also bumps the documentation level from 60.3% to 63.5%.

Before:

Homebrew::CLI::Args instance methods after:

[dduugg]

Resolves

[warn]: In file `extend/hash/deep_transform_values.rb':12: Cannot resolve link to person: from text:
	...{person: {name: “ROB”, age: “28”}...

[MikeMcQuaid]

Much nicer, great work @dduugg!