Update Plausible script (#738)
### Prerequisites
Put an `x` into the box(es) that apply:
- [ ] This pull request fixes a bug.
- [x] This pull request adds a feature.
- [ ] This pull request introduces breaking change.
### Description
Fixes an issue with the Plausible script not loading. As per the
[docs](https://plausible.io/docs/plausible-script), it should be
`script.js` and not `plausible.js`.
**Update:** After further testing (CSP appeared to be the issue), it
looks like it also works with `plausible.js`, probably through backwards
compatibility. If needed, for consistency, this can still be updated to
`script.js`.
### Issues Resolved
Related to #388. It looks like they updated it from `plausible.js` to
`script.js`.
### 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
- [x] 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
Nour Agha