Make the received text read only

[Jacalz]

Checklist

• I have searched the issue tracker for open issues that relate to the same feature, before opening a new one.
• This issue only relates to a single feature. I will open new issues for any other features.

Is your feature request related to a problem?

You can currently edit the text that you get in the window with received text. The code guards against this so that any copy to clipboard or save to file operation still uses the original data. We should instead just make the data read only. Might avoid having to copy the data.

Describe the solution you'd like to see.

Extend the entry and only allow ctrl, shift and arrow keys to pass through. Will likely need to overwrite the cut and paste shortcuts as well.