Merge "dev" into "master"

[unclechu]

Changelog:

• Add nix section to stack.yaml
• Build with LLVM backend by default
• Add FN keys up to F24
• Implement --reset-by-real-escape option
• Implement --ergonomic-ergodox-mode option
• Implement --right-super-as-space option
• Implement --f24-as-vertical-bar option
• Fix bug with not released Control key when toggled Caps Lock by pressing Caps Lock + Enter after an additional Control combo with not released either Caps Lock or Enter
• Use GHC 8.8.2 (by using Stackage LTS-15.0)