const str1: EasingString = 'power2-in'; // valid (matches PresetLinearEasingKey)
const str2: EasingString = 'expo-in-out'; // valid (matches PresetLinearEasingKey)
const str3: EasingString = 'cubic-bezier(0.25, 0.1, 0.25, 1)'; // valid (matches string and is also a valid <easing-function>)
const str4: EasingString = 'ease-in'; // valid (matches TrivialCssEasingFunction)
const str5: EasingString = 'expo'; // valid (matches string) but will lead to a runtime error
const str6: EasingString = 'cubic-bezier(0.25, 0.1, 0.25)'; // valid (matches string) but will lead to a runtime error
Autocompleted custom preset easing strings and trivial
<easing-function>s (but still allowing anystringto account for non-trivial<easing-function>s such as cubier-bezier functions).