Support start/end timezones for Google provider

[guillenotfound]

Additionally I did some minor formatting but we can discard that if you don't like it.

Off topic:

• Generally speaking I think it would make sense to use types over interfaces
• I don't think there should be a snapshot for providers which doesn't support an specific functionality
• start & end should have more restrictive types on a type level (even if that doesn't make any difference)
• Is there any reason not to use URL and any other related constructors to replace stringify fn?

[AnandChowdhary]

Thank you for your hard work on this, really appreciate it! Does it make sense to rename the variables startTimeZone and endTimeZone to make it clearer, what do you think?

[guillenotfound]

Sorry @AnandChowdhary , missed the notification. Updated as per your suggestion 👍