fixed quick links responsiveness (#4488)

## What type of PR is this? (check all applicable)

- [ ] Refactor
- [ ] Feature
- [x] Bug Fix
- [ ] Optimization
- [x] Documentation Update
- [ ] Community Node Submission


## Have you discussed this change with the InvokeAI team?
- [x] Yes
- [ ] No, because:

      
## Have you updated all relevant documentation?
- [x] Yes
- [ ] No


## Description
There was an issue with the responsiveness of the quick links buttons in
the documentation.

## Related Tickets & Documents

- Related Issue #4455
- Closes #4455

## QA Instructions, Screenshots, Recordings

• On the documentation website, go to the Home page, scroll down to the
quick-links section.

[Home - InvokeAI Stable Diffusion Toolkit
Docs.webm](https://github.com/invoke-ai/InvokeAI/assets/92071471/0a7095c1-9d78-47f2-8da7-9c1e796bea3d)

## Added/updated tests?

- [ ] Yes
- [x] No : _It is a minor change in the documentation website._

## [optional] Are there any post deployment tasks we need to perform? No

docs/index.md

@@ -15,7 +15,8 @@ title: Home
 <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@fortawesome/fontawesome-free@6.2.1/css/fontawesome.min.css">
 <style>
     .button {
-      width: 300px;
+      width: 100%;
+      max-width: 100%;
       height: 50px;
       background-color: #448AFF;
       color: #fff;
@@ -27,8 +28,9 @@ title: Home
 
     .button-container {
       display: grid;
-      grid-template-columns: repeat(3, 300px);
+      grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
       gap: 20px;
+      justify-content: center;
     }
 
     .button:hover {