remove most uses of as any in typescript

- replaced many uses of `as any` with another more specific cast `as T`
- filled in missing typed for items that needed to be typed
  - new runtime code was added where necessary to satisfy the new types with comments
- added missing theme variable "sidebar-active" to the Theme variables
- forms using `react-hook-form` are now typechecked
- changed some instances of `target` into `currentTarget` while removing `as any` assertions

src/context/Settings.tsx

@@ -15,8 +15,8 @@ import { Children } from "../types/Preact";
 import { createContext } from "preact";
 import { useMemo } from "preact/hooks";
 
-export const SettingsContext = createContext<Settings>({} as any);
-export const SoundContext = createContext<(sound: Sounds) => void>({} as any);
+export const SettingsContext = createContext<Settings>({});
+export const SoundContext = createContext<((sound: Sounds) => void)>(null!);
 
 interface Props {
     children?: Children,