[misc] Add a note that web worker doesn't support navigator language

There is an Intent to Implement in blink-dev mailing list:
navigator.language(),navigator.languages() and languagechange event for web workers.
[usecase-wrt]update check db to pkginfo --listpkg

[Detailed commit message (if have)]
Impacted TCs num(approved): New 0, update 2, deleted 0
Unit test platform: [tizen]
Unit test result summary: Pass 2, Fail 0, Blocked 0
[wrt] Update json and steps with Crosswalk 8 standard
Merge pull request #750 from kangxu/kangxu/wrt/wrtcases/update

[wrt] Update json and steps with Crosswalk 8 standard
Merge pull request #763 from linshen/shen/misc/add-version

[usecase-wrt]update check db to pkginfo --listpkg
Merge pull request #764 from zqzhang/zqzhang/navigator-language-workers

[misc] Add a note that web worker doesn't support navigator language