Add command to show suggestions window

[antistic]

Summary of changes

Add {PLOVER:SUGGESTIONS} to show the suggestions window in the same way as {PLOVER:LOOKUP} does with the lookup window.

(partially addresses) #645.

To fully address the issue we could add a {PLOVER:SUGGESTIONS_TOGGLE} or {PLOVER:SUGGESTIONS_CLOSE} (which wouldn't be too hard), but then we would likely also want it for other windows e.g. {PLOVER:LOOKUP_TOGGLE}. It may be better to instead address why {PLOVER:SUGGESTIONS}{#Escape} doesn't work on all DE/WMs.

Pull Request Checklist

• Changes have tests ➡️ happy to add these if given pointers as to what kind of test
• News fragment added in news.d. See documentation for details ➡️ Not sure what category this falls under so I haven't done this yet

[user202729]

Likely because the suggestion window appears too quickly. If there's something like {#sleep 2000} (this is another issue...) that could fix the issue.

Or the issue could be that they're on different windows/workspaces.

There's also a related pull request, that adds a delay between every key presses, which would probably also fix the issue.

Currently there's no test for the GUI related stuff. (that having said, I'm not a official Plover maintainer)

[user202729]

Remark: apparently this breaks some plugin (in particular, plover_engine_server), which relies on the list of all hooks.

On the other hand, this can be considered just a minor change, because all programs will break if they rely on the list of all functions provided by an API to work correctly.