Add templating example with tera

[milesgranger]

Presently, there are no examples demonstrating rendering HTML; this PR addresses that.

Description

Added an example using tera which renders some variables into a template.

Motivation and Context

Conveys a concise way to render a HTML response with Tide.

Relates to #207, and might even close it?

How Has This Been Tested?

Verified functionality locally, and passes tests

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[yoshuawuyts]

Thanks heaps for this PR -- commented on a few nits, but think this is a great direction!

[milesgranger]

My pleasure! I've made the updates, per your request. Guess I've gotten into the habit of doing unwraps and expects for demo / examples, but I like your way of thinking; should set a good example. 🎩

Please let me know if there is anything else I should update.

[yoshuawuyts]

💯