Switch templating to Tera

[Kixiron]

The current templates have lots of redundancy, breaking things into smaller units will help with consistency across pages and maintainability

[Kixiron]

This has now changed slightly, I've been investigating the tera templating engine as a suitable replacement for handlebars

[jyn514]

Motivation for tera, as discussed on discord:

• hot reloading so that modifying templates isn't as painful
• inheritance in templates
• more processing done in templates instead of code so we can use more derive(Serialize)
• better docs

[Kixiron]

All of that culminates into what at the end of the day is better, more modifiable and more maintainable code, which is a bonus on every front

[pietroalbini]

I'd also be in favor of moving to tera.