fix: web builder adds null terminator

[brandonpaiz]

In release 1.2, the web UI shows the string "resume" in the web UI. Image: https://i.imgur.com/NbEYPMR.png

This is because

1. there is no null terminator in the array constructed by src/scripts/build_web_ui.sh
2. We pass this array directly to a String constructor when the web ui is requested
3. The String constructor doesn't provide options for array length and expects it to be null terminated.

Easiest solution: have build_web_ui.sh append a null byte

[AlexLynd]

Goddamn do i hate regex patterns, but this looks good to me!

[brandonpaiz]

Some of my favorite bugs come from regex related issues :)