Request: fn_toggle support on Razer Blade 15 2018

[danryu]

As per @z3ntu's request (https://github.com/openrazer/openrazer/issues/1154) I am opening an issue here to get visibility on this issue.

Same issue as at https://github.com/polychromatic/polychromatic/issues/218

Problem: Lack of fn_toggle support

If I'm not mistaken, the "fn_toggle" refers to the Function key being "toggled" to its inverse state, meaning that the Fn key does not have to be pressed to operate the multimedia section, ie volume up/down can be pressed with F2 and F3 only, screen brightness up/down with F8/F9 only, and so on.

In the Windows app Synapse, the feature is referred to as "Function Key Primary". It would be a MASSIVE help to me (and many other Linux Blade users I'm sure) to have this enabled, as it makes using those essential functions in different environments MUCH easier - operating the Mute button with one finger, for example, would be very handy!

I've attached a pic of the Synapse feature so you can see the context.