Define a different timezone for scheduled tasks

[delyriand]

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	yes
Fixed issue	#...
License	MIT

As explained in the README, this PR lets you define a different timezone for scheduled tasks.

For example, I'm using the UTC timezone in my PHP config, but I want my scheduled tasks to be launched on the Paris timezone. I change the value of the env variable in a .env:

SYNOLIA_SCHEDULER_PLUGIN_TIMEZONE=Europe/Paris

[CLAassistant]

All committers have signed the CLA.

[delyriand]

@oallain what do you think of this proposal?

[oallain]

@oallain what do you think of this proposal?

Hello, I think it's a good feature, we just need to fix CI.