Add keyboard shortcuts for icons in the editor

[muddi900]

Short description

Add shortcuts for Adding icons in the editor.

Proposed changes

• Pressing Alt+|+<number> would insert the corresponding icons
• The sequence corresponds to the sequence in menu. eg. 1 for pin, 2 for www, etc.

Side effects

• None

Resolved issues

Fixes: #1957

---

Pull Request Review Guidelines

[MizukiTemma]

Congratulation for your first PR in our repository 🎉 It's almost there 😃

Additionaly to the suggestion in the code, I would like you to add an entry into CHANGELOG file under UNRELEASED.

[MizukiTemma]

Very cool! Thank you 😃

After squashing the commits (and resolving conflicts if any occurs) I think this PR is ready to be merged 👍

[PeterNerlich]

Looks good to me, works as expected. Congrats!

[timobrembeck]

Thanks a lot, really cool feature! 👍

After squashing the commits

I agree, could you execute:

git rebase --interactive HEAD~2

and replace the second "pick" by "fixup" and save?
Then, you'd have to do:

git push --force-with-lease

To overwrite the existing commits.

Additionaly to the suggestion in the code, I would like you to add an entry into CHANGELOG file under UNRELEASED.

Again, I agree, and this change has not yet been addressed.
Could you add the lines:

* [ [#1957](https://github.com/digitalfabrik/integreat-cms/issues/1957) ] Add keyboard shortcuts for icons in the editor

to the CHANGELOG.md into the UNRELEASED section?

[timobrembeck]

Thanks a lot! 👍
I rebased your branch one last time and cleaned up the git history, now I think this is good to go! 🎉

(One optional idea I had was to somehow document this possibility, otherwise users don't know the keyboard combinations for the icons, but I guess we can also put this in our usage wiki.)