Add tab cycling with ctrl[+shift]+tab or ctrl+[pageup|pagedown]

[GustavoKatel]

This is related to #35

Description

This PR adds the following key bindings:

• ⌘+pagedown, ctrl+pagedown, ⌘+shift+tab, ctrl+shift+tab: set active the next service
• ⌘+pageup, ctrl+pageup, ⌘+tab, ctrl+tab: set active the previous service

This is not set in stone. These settings are comfortable to me, but I am free to discuss the semantics of each key-binding.

Motivation and Context

Since this feature exists in Franz 4 and it makes Franz 5 UX richer, I don't see why not 😛

How Has This Been Tested?

OS: Linux Mint 18.2 (Ubuntu 16.04)
I cannot test on others environment. Can you guys help me with this?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• [x ] New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project (run $ yarn lint).

[GustavoKatel]

Just noticed now that it was cycling through disabled services as well, which are not mount by react, therefore causing an error. All fixed.

[tobiasdueser]

Wouldn't it be more intuitive if ctrl+tab would cycle down and ctrl+tab+shift up? Like the direction of reading: left to right and top to bottom.

[GustavoKatel]

This is tricky @tobiasdueser 😃 It seems more intuitive to me that way. If this is a deal-breaker and since this PR is merged, you could open an issue with a feature request.