Add all exit statuses to docs for cargo check

[DidingasLushis]

Problem

Hello there, when cargo checking features that are invalid I get an exit status of 101 and I went to:
https://github.com/rust-lang/cargo/blob/master/src/doc/src/commands/cargo-check.md

To understand this exit code compared to others it would be nice to have a table of the expected exit codes and their meaning.

Proposed Solution

Code	Meaning
0	Check Passed
101	Invalid Features
X	Meaning X

Notes

Where could I find the returned codes, I would be happy to make this change, however the experienced contributor reading this could likely do so in 10 seconds.

[weihanglo]

They are listed here already:

cargo/src/doc/src/commands/cargo-check.md

Lines 411 to 414 in a6c58d4

	## EXIT STATUS
	* `0`: Cargo succeeded.
	* `101`: Cargo failed to complete.

So I guess that should be sufficient?

BTW, in Cargo we tend not to extend more exit status code. The standard way to understand an error is via --message-format=json, though for Cargo its own message it is still in design phase, see #8283.

[epage]

iirc we also return 1 for CLI errors though unsure how intentional that is. Whether something is a CLI error or not is a bit of a blurry line and changes over time.

[DidingasLushis]

I missed that entry my bad, but it sounds like based on @epage there might be missing arms?

(Yeah it's there)