Added a script category to New File, with appropriate directory structure

[kwekmaster]

Implemented

New Redscript file. (Click spoiler to see image)

New CET Lua file. (Click spoiler to see image)

Implementation Notes:

• Scripts is the category for both. Because that's what they are: scripts.
• GetDefaultDir is still set to the resources directory. I added the full path to the FileName instead. This allows better control for script writers who (hopefully) has a bit more knowledge on where these things go. IMHO this strikes a good balance between UX and usability.
• That said, I tacked on the project's name as starting directory for the scripts in the FileName. User can change this manually.
• I didn't care too much for the file icons since it doesn't impact functionality. *.reds has a pre-existing icon, but CET lua doesn't have it. Let me know if you have any preference/want me to assign an icon for it.

Testing

• Intended functionality testing. Done--works as intended.
• Integration. Done, undisturbed. e.g. my screenies above show what happens if the file already exist.
• Existing functionality testing. Done, also undisturbed.

[rfuzzo]

lgtm thanks