Sync variable-length-quantity exercise (issue #976)

[resu-xuniL]

Sync variable-length-quantity (issue #976)

• Synced variable-length-quantity metadata and docs
• Removed strict types comments from example.php and VariableLengthQuantityTest.php
• Added variable-length-quantity to auto-sync.txt
• Added UUID and TestDox to tests
• Added GitHub handle to config.json

(I kept A-O-Emmanuel in 'contributors' section as I just continue his work)

Closes #976

[github-actions]

This PR touches files which potentially affect the outcome of the tests of an exercise. This will cause all students' solutions to affected exercises to be re-tested.

If this PR does not affect the result of the test (or, for example, adds an edge case that is not worth rerunning all tests for), please add the following to the merge-commit message which will stops student's tests from re-running. Please copy-paste to avoid typos.

[no important files changed]

For more information, refer to the documentation. If you are unsure whether to add the message or not, please ping @exercism/maintainers-admin in a comment. Thank you!

[mk-mxp]

So many conversions, I hope your hex calculator isn't broken now...

[mk-mxp]

Thanks a lot for this contribution!

[resu-xuniL]

You're welcome!