ChatAPI functionality

[sotoz]

Added actions for Chat API.

• Chat Channels Create/Delete/Update/List all/View one
• Chat Contacts Create/Delete/List all/View one
• Chat Messages Create/List all/View one
• Chat Platforms List all

Created examples for every needed action.

[samwierema]

My first instinct is that I would separate all Chat API-related objects and resources into their own sub-namespace. So where it's now MessageBird\Objects\ChatChannel I would feel we should make clear it's a separate API (and can thus behave differently) by putting it in it's sub-namespace, e.g.: MessageBird\Objects\Chat\Channel.

[bviolier]

I agree with @samwierema

[sotoz]

Should we do it only for the Chat related objects?

[samwierema]

@sotoz yes, everything else should remain in place.

[dstotijn]

Dummy access key contains tab character.

[dstotijn]

Please also check for double newlines (maybe run phpcs with PSR2)?

[gedimin45]

should this be updated during release somehow?

[gedimin45]

no example to create contacts?

[sotoz]

platformId will be corrected.
Example for creating contacts not needed. Contacts are being created automatically when the first message arrives.