Previously, there were a few places where the compiler would create
strings from template content and emit them as template literals, but
didn't properly escape characters or character sequences with special
meanings, in particular: backslashes, backticks, and interpolation
sigils.
This commit fixes this in:
- block creation (interpolation sigils were not escaped)
- text node creation (no escaping was performed)
- comment not creation (no escaping was performed)
- default values for t-esc (no escaping was performed)
- body of a t-set (no escaping was performed)