post https://a.klaviyo.com/api/templates/
Create a new custom HTML template.
If there are 1,000 or more templates in an account, creation will fail as there is a limit of 1,000 templates
that can be created via the API.
Request specific fields using sparse fieldsets.
Rate limits:
Burst: 10/s
Steady: 150/m
Scopes:
template:write