[Feature request] Edit entry/clipboard content

[stellarix]

Quite useful to be able to edit clipboard content and saved it, like what Klipper from KDE can do.
I often use this feature to correct typo/error or change some text in the content, that way users don't have to add a new entry everytime they want to change something in the clipboard.

[Tudmotu]

I like this feature.
While I most likely won't have time to implement something like this myself, I would accept a PR for this.

So the idea is to add an icon like that for every text entry (not images), then open up a popup with the text inside to be edited.

This PR might be large and require some thorough review, but if anyone is up for the challenge, I will help them with implementing this.