Add new feature to base.plugin.bash

[TheMadTomato]

Description

New function labeled rex() servers a single purpose. Replace the file extensions of multiple file at once. File extensions usually does not quite matter in bash, but there is a few cases when one might needs to and this function simplifies the process from multiple commands into one.

The Function

function rex() {
	about 'mass replace of the extension of multiple files'
 	param '1: extension to replace'
  	param '2: new extenstion'
   	example 'rex txt md'
    	group 'base'
	local ext2replace="${1:-}"
 	local newext="${2:-}"
  	local files=(`ls *.$ext2replace`)
   	for file in "${files[@]}"; do mv "$file" "${file/%.$ext2replace/.$newext}"; done
}

How Has This Been Tested?

Created multiple test files with different extensions, than proceeded to use rex to only change the specified extension which worked flawlessly

Testing Environment

• OS : Debian GNU/Linux 12 (bookworm) x86_64
• VER: 6.1.0-21-amd64
• Bash Ver: 5.2.12
• Computer: Lenovo Thinkpad P52s

Screenshots (if appropriate):

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [x] If my change requires a change to the documentation, I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] If I have added a new file, I also added it to clean_files.txt and formatted it using lint_clean_files.sh.
• [ ] I have added tests to cover my changes, and all the new and existing tests pass.