fix: Use `x` instead of `tweet` in exampleSite (#996)

### Prerequisites

Put an `x` into the box(es) that apply:

- [x] This pull request fixes a bug.
- [ ] This pull request adds a feature.
- [ ] This pull request introduces breaking change.

### Description

Changes exampleSite to use `x` instead of `tweet`

### Issues Resolved

Newer versions of Hugo complain upon seeing `tweet`:
```
ERROR The "twitter", "tweet", and "twitter_simple" shortcodes were deprecated in v0.142.0 and removed in v0.156.0. Please use the "x" shortcode instead.
```

### Checklist

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#### General

- [x] Describe what changes are being made
- [x] Explain why and how the changes were necessary and implemented
respectively
- [ ] Reference issue with `#<ISSUE_NO>` if applicable

#### Resources

- [ ] If you have changed any SCSS code, run `make release` to
regenerate all CSS files

#### Contributors

- [x] Add yourself to `CONTRIBUTORS.md` if you aren't on it already