docs: Add documentation on how to contribute a Vector DB provider and update testing documentation (#3093)

# What does this PR do?

- Adds documentation on how to contribute a Vector DB provider.
- Updates the testing section to be a little friendlier to navigate.
- Also added new shortcut for search so that `/` and `⌘ K` or `ctrl+K`
trigger search


<img width="1903" height="1346" alt="Screenshot 2025-08-11 at 10 10
12 AM"
src="https://github.com/user-attachments/assets/6995b3b8-a2ab-4200-be72-c5b03a784a29"
/>

<img width="1915" height="1438" alt="Screenshot 2025-08-11 at 10 10
25 AM"
src="https://github.com/user-attachments/assets/1f54d30e-5be1-4f27-b1e9-3c3537dcb8e9"
/>

<!-- If resolving an issue, uncomment and update the line below -->
<!-- Closes #[issue-number] -->

## Test Plan
<!-- Describe the tests you ran to verify your changes with result
summaries. *Provide clear instructions so the plan can be easily
re-executed.* -->

Signed-off-by: Francisco Javier Arceo <farceo@redhat.com>

docs/_static/js/keyboard_shortcuts.js

@@ -0,0 +1,14 @@
+document.addEventListener('keydown', function(event) {
+  // command+K or ctrl+K
+  if ((event.metaKey || event.ctrlKey) && event.key === 'k') {
+    event.preventDefault();
+    document.querySelector('.search-input, .search-field, input[name="q"]').focus();
+  }
+
+  // forward slash
+  if (event.key === '/' &&
+      !event.target.matches('input, textarea, select')) {
+    event.preventDefault();
+    document.querySelector('.search-input, .search-field, input[name="q"]').focus();
+  }
+});