[Data] Add Vale configuration

[bveeramani]

Why are these changes needed?

This PR adds configuration for Vale -- a linting tool that helps us enforce a consistent editorial style. To use Vale, either install the VSCode extension for Vale or run vale doc/source/data.

In a future PR, we plan to enforce Vale in CI (starting with the Data documentation).

Related issue number

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

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[angelinalg]

This literally gives me the warm fuzzies. Thank you so much, @bveeramani and @amogkam!

One request, @bveeramani, is there a way to standardize how we tell readers to "see" another doc, vs "read, go to, check out, etc."

[angelinalg]

Just some nits.

[amogkam]

All credit goes to @bveeramani! Great work!

[amogkam]

data doc changes lgtm