Add ".pwn" to the official list of extensions.

[Y-Less]

What this PR does / why we need it:

Adds ".pwn" to the list of include extensions. It is used by almost all scripts, so why shouldn't it be officially supported?

Which issue(s) this PR fixes:

Fixes #

What kind of pull this is:

• [ ] A Bug Fix
• [x] A New Feature
• [ ] Some repository meta (documentation, etc)
• [ ] Other

Additional Documentation: