Variable interpolation

[dpeckham]

See https://github.com/pagerguild/vhs?tab=readme-ov-file#type

Env NAME "Emmanuel Goldstein"
Type "Hello, ${{NAME}}!"

Would you like me to create a PR?

Dave

[baumandm]

I wanted to generate timestamped screenshots using VHS, and rewriting my tape every time was a pain. So I put together an implementation for this behind an optional config. For example:

Set EnvExpansion true

Screenshot "screenshots/demo-{{TIMESTAMP}}.png"

Then run with

TIMESTAMP="$(date '+%Y-%m-%d %H:%M')" vhs demo.tape

I went with {{VAR}} instead of $VAR to avoid ambiguity with Type "echo $HOME" where you want the literal text typed.

My use case is screenshots but you could use this to parameterize typed text as well as other commands.

My changes are here, happy to turn this into a PR.