support common test framework global API

[crusoexia]

Nowadays dev spent half time to read/write/fix UTs, so it would be nice to have the common test apis highlighted.

current yats test file:

js file highlighted by vim-javascript:

These keyword are good highlight candidates:

describe it test before after beforeEach afterEach beforeAll afterAll expect assert

[crusoexia]

@HerringtonDarkholme Sorry I want to bring this back to table. These keywords are marked as typescriptGlobal, however, they are not part of typescript but apis provide by common test frameworks as jest mocha chai etc., could you give these keywords another identifier other than typescriptGlobal? How about typescriptTestKeywords? With different identifier colorschemes can set different color to the different things.

Thanks

[HerringtonDarkholme]

Pull request is welcome.

[crusoexia]

Created. Let me know if anything is not match the convention.