Fix comments

[nielsbasjes]

Update

• Template - Update existing .gitignore templates

Details

While working on my gitignore reader https://github.com/nielsbasjes/codeowners I ran into problems while using the templates that originated from here as a testing reference.

There are several places where the author of the template intended to create a comment but did not. The root cause is that in a .gitignore file a comment starts with a # as the first character on a line. In all other places it is NOT interpreted as a comment.

https://git-scm.com/docs/gitignore#_pattern_format states

A line starting with # serves as a comment. 
Put a backslash ("\") in front of the first hash for patterns that begin with a hash.

I have verified this with the Dart.gitignore which has

*.js             # When generated by dart2js. Don't specify *.js if your

If I create a test.js it is not ignored by git.

I have checked all cases found by this:

find . -type f -name '*.gitignore' | xargs grep -v '^#' | fgrep '#'

Notes

This is 2 commits. One for the imported files from github and one for the files in this repo.
I have submitted these exact changes to github github/gitignore#4394 but it seems that repo has been unmanaged for over a year now.