Docs: Update CLA link and add it to PR template

[davidlj95]

Pull request checklist

Make sure you:

• [x] Signed the Contributor License Agreement (after creating PR)
• [x] Followed the commit message guidelines

For non-trivial changes, please make sure you also:

• N/A Added/Updated related documentation.
• N/A Added/Updated related tests.

Short description of the change(s)

After looking for the CLA in docs for my first contribution found out the only reference to it had a link that didn't work (domain doesn't exist). Fixing that link + adding a link in PR template so impatient contributors like me can browse the CLA whilst the CLA signing comment appears.

[molant]

/AzurePipelines run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 1 pipeline(s).

[vidorteg]

/azp run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 1 pipeline(s).

[vidorteg]

[Doing some cleaning]. Unfortunately and due to me missing to review this 😓the proposed url has gone also stalled. feel free to reopen pointing to the new one, or I can also do it if needed. thanks again for the contribution and sorry that this went missed.

[davidlj95]

No problem at all @vidorteg :) just reopened with new link here: https://github.com/webhintio/hint/pull/5751