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