Adding Link Checker

[anarnold97]

This PR should implement a GitHub action that checks files for broken links.

The script is built with the following inputs:

Section	Script	Explanation
Event Trigger	on: [pull_request]	Specifies that this workflow should run automatically whenever a pull_request event occurs (e.g., when a pull request is created, synchronized, or reopened).
Workflow Name	name: Check links for modified files	A descriptive name for the entire workflow, visible in the GitHub Actions tab.
Jobs Definition	jobs:	Begins the definition of the tasks (jobs) that will execute in the workflow.
Job ID	markdown-link-check:	The unique identifier for this specific job.
Runner Environment	runs-on: ubuntu-latest	Defines the environment where the job will execute—in this case, the latest version of an Ubuntu Linux virtual machine hosted by GitHub.
Steps Definition	steps:	A sequence of individual tasks (steps) to be executed within the markdown-link-check job.
Step 1: Checkout	- uses: actions/checkout@v4	Uses the official checkout action to download the repository's code onto the runner environment so the subsequent steps can access the files.
Step 2: Link Checker	- uses: gaurav-nelson/github-action-markdown-link-check@v1	Executes a third-party action designed to check links within files.
Action Inputs	with:	Passes configuration parameters (inputs) to the link-checking action.
Quiet Mode	use-quiet-mode: 'yes'	Instructs the link-checking action to suppress non-essential output. (Note: This setting might be overridden or combined strangely with verbose mode depending on the action's logic).
Verbose Mode	use-verbose-mode: 'yes'	Instructs the link-checking action to print detailed output, which usually includes more information about the checking process and any encountered errors.
Target Files	check-modified-files-only: 'yes'	This is the crucial setting: it tells the link checker to only check links in Markdown files that were modified as part of the current pull request (i.e., the files that are different between the base branch and the PR branch). This makes the check much faster and more focused.

Once merged it will create a new GitHub action.

[mpershina]

Looks great and very useful! TY, Andy!