Injecting into *.pug fies doesn't work while does for *.jade

It looks like those are not detected by the file extension and considered as default htmls, since if I use e.g. injection happens in html format.

Start by tracing how gulp-inject detects template extensions and compare the existing .jade path with .pug handling. Reproduce the issue with a .pug file containing the documented injection comment, then verify that the expected injection occurs for Pug without changing HTML behavior.

Written by the indexing model from the issue text.