fix: improve accessibility of links by adding an underline (#288)

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## PR Checklist

- [ ] Addresses an existing open issue: fixes #000
- [ ] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/boston-ts-website/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/boston-ts-website/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

<!-- Description of what is changed and how the code change does that.
-->

Essentially, per WCAG 2.1 Techniques:

> Link underlines or some other non-color visual distinction are
required (when the links are discernible to those with color vision).

References:
- https://www.w3.org/WAI/WCAG21/Techniques/failures/F73
-
https://accessibleweb.com/question-answer/do-links-need-to-be-underlined/
- https://webaim.org/techniques/hypertext/link_text

We might also want to consider a different color for links:
https://www.w3.org/WAI/WCAG21/Techniques/general/G183

Before | After
--- | ---
<img width="1512" alt="Screenshot 2024-06-28 at 02 05 54"
src="https://github.com/SquiggleTools/boston-ts-website/assets/113730/e4a4d605-7ea5-4c7f-b86c-b4ea10cdb32f">
| <img width="1512" alt="Screenshot 2024-06-28 at 02 06 08"
src="https://github.com/SquiggleTools/boston-ts-website/assets/113730/d10c77e9-7ddb-45cc-ba6d-b29c6f5924e0">

app/raw.css

@@ -29,5 +29,4 @@ p {
 :link,
 :visited {
 	color: inherit;
-	text-decoration: none;
 }