Add CI job to add docs to Github pages

[echeran]

Closes #111

[coveralls]

Pull Request Test Coverage Report for Build 14ee6e9f6f85d3667ed9023db482105ba3754950-PR-160

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.3%) to 90.758%

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Files with Coverage Reduction	New Missed Lines	%
components/locale/src/extensions/transform/key.rs	2	90.0%
components/locale/src/extensions/unicode/key.rs	2	90.91%

Totals
Change from base Build 1e3b00ea3b0456993de8f1f2ee0b4cbfb90ddc7f:	-0.3%
Covered Lines:	1149
Relevant Lines:	1266

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💛 - Coveralls

[sffc]

Cool!

Are the docs posted yet for preview?

Why does it say "this check was skipped"?

[echeran]

I forgot to mention that. The URL is: https://unicode-org.github.io/icu4x-docs/

It says the check was skipped b/c it only runs on master, not PRs,. I mentioned over in the issue that PRs (which are WIP) shouldn't be allowed to clobber the latest version of our docs based on our code from master, which has passed review.

[sffc]

Why does https://unicode-org.github.io/icu4x-docs/icu4x/ show all of our dependencies as crates? Is there a way to fix that?

[filmil]

Why does https://unicode-org.github.io/icu4x-docs/icu4x/ show all of our dependencies as crates? Is there a way to fix that?

Looks like cargo is able to omit dependencies if specifically asked to do so:
https://stackoverflow.com/questions/34215411/how-do-i-prevent-rust-doc-from-adding-dependencies-to-documentation

[echeran]

Yep, thanks for the link. The new commit adds the --no-deps arg. A test on my personal fork shows the cleaned up docs in the docs repo at https://echeran.github.io/icu4x-docs/.

[sffc]

Optional: I don't know when you decide to lump things into "build-test.yml" and when you split things into new files like you did with "coverage.yml". Personally, I think docs deserve their own file.

[echeran]

I initially considered a separate workflow, but then I confirmed the fact that workflows cannot depend on each other. Only jobs within a workflow can depend on each other. And I don't want the docs to be generated if the code doesn't build / tests don't pass.

And since formatting is quicker thing to check than doc generation but is required for all commits, I also made that a dependency of docs too so that we don't generate docs needlessly when formatting needs cleanup. (I guess docs are generated from parts of code that adhere to a certain format, so that docs generation job dep on formatting should make sense for that reason, too.)