PowerRename: Convert case / uppercase, lowercase, etc.

## 📝 PowerRename: Convert case / uppercase, lowercase, etc.

Add ability to convert case to uppercase/lowercase, etc.

The simplest solution I feel would be to use regex-style matching, with some special syntax to indicate case conversion:

For example:
Match: `(.*) is a (.*)`
Replace: `$lowercase($1) is a $uppercase($2)`

Match: "THIS is a test."
Result: "this is a TEST"