fix(no-useless-mustaches): escape < in fixes

[DMartens]

Fixes #2384 I looked up the parser specification for the inside tag case for potential additional cases which would differ:

• <: already covered in the issue
• EOF: would already be an error
• \0: I guess/hope no one would do this but there is a difference
• &: there are cases when combining the text with either before or after the mustache but is also highly unlikely

So this PR only adds escaping < with < in the fixer.

[FloEdelmann]

There is still a lint error, so please run npm run lint:fix.