CI: add Vale to apply Google style guide to all md files

[CharLotteiu]

What is changed, added or deleted? (Required)

Add Vale in CircleCI to apply the Google developer documentation style guide to all md files in the repo.

Vale is highly customizable so it is possible for us to set our own rules in yaml files according to our needs.

Which TiDB version(s) do your changes apply to? (Required)

• [x] master (the latest development version)
• [x] v4.0 (TiDB 4.0 versions)
• [x] v3.1 (TiDB 3.1 versions)
• [x] v3.0 (TiDB 3.0 versions)
• [x] v2.1 (TiDB 2.1 versions)

What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s): Customized Vale rules of CRDB https://github.com/cockroachdb/docs/tree/master/ci/vale

Do your changes match any of the following descriptions?

• [ ] Delete files
• [ ] Change aliases
• [ ] Have version specific changes
• [ ] Might cause conflicts

[yikeke]

Can you try and run the vale check against all markdown files? Right now it only reports issues against the two test files. @CharLotteiu We'd like to see the whole picture of what language and style issues we've got in this repo.

[ti-srebot]

@lilin90, @yikeke, PTAL.

[ti-srebot]

@lilin90, @yikeke, PTAL.

[ti-srebot]

@lilin90, @yikeke, PTAL.

[yikeke]

/hold

[ti-chi-bot]

@CharLotteiu: PR needs rebase.

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[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

:white_check_mark: CharLotteiu
:x: yikeke

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[qiancai]

Removed the needs-cherry-pick-release-2.1 label because the v2.1 docs have been archived at https://docs-archive.pingcap.com/tidb/v2.1 and will no longer receive new updates.

[qiancai]

Removed the needs-cherry-pick-release-3.1 label because the v3.1 docs have been archived at https://docs-archive.pingcap.com/tidb/v3.1 and will no longer receive new updates.

[qiancai]

Removed the needs-cherry-pick-release-3.0 label because the v3.0 docs have been archived at https://docs-archive.pingcap.com/zh/tidb/v3.0 and will no longer receive new updates.

[ti-chi-bot[bot]]

@CharLotteiu: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-verify	3f2dfd6f94f5e40c857bb24721f19afefe39a2ca	link	true	/test pull-verify

Full PR test history. Your PR dashboard.

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[qiancai]

Removed the needs-cherry-pick-release-4.0 label because the v4.0 docs have been archived at https://docs-archive.pingcap.com/tidb/v4.0 and will no longer receive new updates.

[qiancai]

Removed the needs-cherry-pick-release-5.0 label because the v5.0 docs have been archived at https://docs-archive.pingcap.com/tidb/v5.0 and will no longer receive new updates.