SAVE THE FORESTS: Comment schedule and recommend for plugins writers to avoid daily builds

[nugged]

dev-koha-plugin-kitchen-sink/.github/workflows/main.yml

Line 9 in 108b43e

- cron: "0 6 * * *"

Why scheduled builds are not needed most of the time:
99% of plugins do not need to be built daily, so this is very unethical burning of coil for all repos and forks, daily, 5 minutes of CPU time, and usually without reason.

... please, commend this and hint all plugin writers to use scheduled build only when there is a reason for it. Moreover: scheduled build even if enabled for a reason, might also happen on forked experiments, which even more not needed.