-E output window

[bates64]

From @Trevor89 on 2021-11-07:

Is it possible to output the pre-processed C (using -E) to the output window if said flag is enabled (might need to use a checkbox so JS knows to switch files)? this would - for me at least- mean that decomp.me replaces all the functionality of querams site. Uses for -E include live macro programming (which I did on querams site before it broke).

[bates64]

Unsure if this is in-scope personally but it seems a fairly easy addition