[tag tool] Feature requests

Small UX tweaks:

- [x] Use Roboto not Avenir (traitor!)
- [x] move the 'save csv' button to the right to separate it from the 'open pull request' button
- [x] give the 'add' button a blue background to raise it in the visual hierarchy as the default end action
- [x] horizontally center align each row

Medium UX tweaks:

- [x] add the https://github.com/adobe-fonts/adobe-notdef font for fallback
- [x] add a simple autocomplete to the family name input