Document TEMPL_DEV_MODE

[flunderpero]

My setup is a bit unusual. I have templ generate --watch running on my dev machine but the app is running in a Docker container. I don't want to run templ generate --watch in the container to keep it as close to production as possible.

I was wondering why text changes were not picked up as "promised" by the documentation until I saw in the source code that TEMPL_DEV_MODE needs to be set to true.

Perhaps it's worth it to add it to the documentation.

[a-h]

Good point! I didn't expect that as a use case.

Happy to take a PR on that!

I'll label this one up as a docs improvement for anyone that fancies it.