enable paste buffer to be changed before pasting

[fdncred]

This PR is just a thought starter. What would it be like to be able to paste data into reedline and have it manipulate that data?

In this example, I paste some shell script syntax and it's changed to nushell syntax.

Input from clipboard:

ENV_VAR1=var1
export ENV_VAR2=var2
line one \
line two \
line three \
line four

Output in reedline command buffer

(note the different env var syntax and the line continuation characters are removed)

I was thinking it would be cool to have some type of hook/callback where in nushell one could provide a custom command/script/module to manipulate data that is pasted. I'm not even sure that it's possible, but like I said, this is a thought starter.

I do not expect this PR to land. Just wanted to use it as an example.

[codecov]

Codecov Report

Merging #652 (b7c9e75) into main (adc20cb) will decrease coverage by 0.68%.
Report is 1 commits behind head on main.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #652      +/-   ##
==========================================
- Coverage   49.76%   49.08%   -0.68%     
==========================================
  Files          41       42       +1     
  Lines        7827     7935     +108     
==========================================
  Hits         3895     3895              
- Misses       3932     4040     +108     

Files	Coverage Δ
src/edit_mode/emacs.rs	88.03% <0.00%> (-5.61%)	⬇️

... and 3 files with indirect coverage changes

[fdncred]

This was fun and has potential but there doesn't seem to be anyone who's interested right now. So, I'll just cloes this for now.