How to Uppercase the First Letter in Jinja?

I have been using Jinja for my side-project and was surprised to find that there’s no way to uppercase only the first letter. There is a capitalize filter but it also lowercases the rest of the letters—something you wouldn’t want if your text has acronyms or proper nouns. Jinja doesn’t support sentence case by default, but thankfully it’s not hard to recreate that.