Make NormalizedHotkeyString extend NormalizedSequenceString

[iansan5653]

A HotkeyString is a valid SequenceString but with only one item in the sequence. So anything that accepts SequenceString should also accept HotkeyString.

This PR makes HotkeyString extend SequenceString to allow for this.

This felt a little backwards to me because sequences are built from hotkeys, not the other way around, but it is correct. I made a simple demo to test it out:

const normalizedHotkeyBrand = Symbol('normalizedHotkey')
export type NormalizedHotkeyString = NormalizedSequenceString & {[normalizedHotkeyBrand]: true}

const normalizedSequenceBrand = Symbol('normalizedSequence')
export type NormalizedSequenceString = string & {[normalizedSequenceBrand]: true}

const hotkey = "a" as NormalizedHotkeyString
const sequence = "a b" as NormalizedSequenceString

const thingsThatAcceptSequencesShouldAcceptHotkeys = (sequence: NormalizedSequenceString) => {}
thingsThatAcceptSequencesShouldAcceptHotkeys(sequence)
thingsThatAcceptSequencesShouldAcceptHotkeys(hotkey)

const thingsThatAcceptHotkeysShouldNotAcceptSequences = (hotkey: NormalizedHotkeyString) => {}
thingsThatAcceptHotkeysShouldNotAcceptSequences(hotkey)
// @ts-expect-error
thingsThatAcceptHotkeysShouldNotAcceptSequences(sequence)

Note

Using string template types for this would solve this problem more elegantly, but that's a lot more complicated and comes with more of a compile-time performance cost. This is 'good enough'.