Add keymaps for start, resume, submit and discard Reviews

[carlos-algms]

Describe what this PR does / why we need it

The process of opening a pull-request and starting a review was a little disconnected, as we had keymaps to almost everything we can do with a pull-request, except for starting a review.

review-keymaps.mp4

Describe how you did it

I followed the project standard and created named mappings that mirror the configuration keys and added them to:

• Pull request buffer (pull_reqest)
• The diff-view of the Review (review_diff)
• The review pane (file_pane)

The new commands are:

Command	Binding
review_start	<leader>vs
review_resume	<leader>vr
submit_review	<leader>vs
discard_review	<leader>vd

Describe how to verify it

Start and resume a PR:

1. Open a Pull-Request
2. press <leader>vs to start a review
3. press Ctrl+c to close the review
4. press <leader>vr to resume the review

Submit or discard a PR

1. Open a Pull-request
2. 2. press <leader>vs to start a review
3. from the diff-view or the files pane, press <leader>vs to open the submit modal
4. Run the command :q to close it
5. press <leader>vd to discard the review, you should see a prompt asking to confirm.

Special notes for reviews

Aside from the keybindings, this PR also fixed the Ctrl+C to close the review, that wasn't working, as it wasn't passing the current tab as an argument to the close() function, so the key press was just ignored.

[pwntester]

LGTM, Thanks for the contribution!