Discord invite codes in README and CONTRIBUTING.md are expired

## Issue

The Discord invite codes linked from the project are dead. Verified against the Discord API:

| Location | Code | API response |
|---|---|---|
| `README.md` (badge link, alt text) | `dAuKfZS` | `{"message":"Invite is expired.","code":50270}` |
| `CONTRIBUTING.md` | `8TW9nfF` | `{"message":"Unknown Invite","code":10006}` |

Reproduce:
```bash
curl -s https://discord.com/api/v9/invites/dAuKfZS
curl -s https://discord.com/api/v9/invites/8TW9nfF
```

Both return non-2xx error bodies as shown above (50270 = expired, 10006 = unknown/revoked).

## Impact

The README badge advertises a "join us on Discord" link that dead-ends. CONTRIBUTING.md compounds this for first-time contributors who follow the doc. There's also an alt-text bug: the badge image alt currently reads "Embark" rather than "Discord", which screen readers will announce incorrectly.

## What I'd need to fix this

A working Discord invite code (or a permanent invite URL) from someone with server membership at the EmbarkStudios Discord. Once you can supply that, I'm happy to open a PR that updates both \`README.md\` (link + alt text) and \`CONTRIBUTING.md\` in one change. Without a live invite I can verify hits Discord successfully, any code I'd put in is a guess.

***

*Filed by [kimjune01/sweep](https://github.com/kimjune01/sweep), an autonomous OSS contribution pipeline. The maintainer of this pipeline reviewed before sending. Hypothesis graph: https://github.com/kimjune01/sweep/blob/master/repo-hypotheses/EmbarkStudios-puffin.md*