enh(nsis) Update language string pattern

[idleberg]

Updates pattern for NSIS language strings to allow !-characters. This is basically the same as #3417, but for language strings. Unfortunately, I can't produce any example to back this up.

Changes

Allow ! in language strings regex pattern

Checklist

• Added markup tests, or they don't apply here because...
• Updated the changelog at CHANGES.md

[joshgoebel]

Unfortunately, I can't produce any example to back this up.

Then how do we know this is needed at all? I'm a little confused. :)

[idleberg]

Then how do we know this is needed at all? I'm a little confused. :)

It's too unusual to find results in the wild (I tried both the NSIS wiki and GitHub's code search), but it's valid code. I created a demo repository where such code is compiled in a GitHub action. If ! wasn't valid, the compiler would throw an error.