Changed the type of the "node" in hooks to be as specific as possible

[reduckted]

Fixes #1029.

Prior to the TypeScript type declarations being provided by this package, the @types/dompurify package defined all hooks as taking an Element as the first parameter. That was incorrect because some hooks can be given a Node or DocumentFragment. When the type declarations were moved into this repository, the hook's first parameter type was changed to Node. This change was overzealous because some hooks are guaranteed to only be given an Element or DocumentFragment.

To account for those hooks, this pull request adds two additional hook types - ElementHook and DocumentFragmentHook (plus Hook has been renamed to NodeHook to disambiguate it).

Hook	Type of currentNode
beforeSanitizeElements	Node
afterSanitizeElements	Node
beforeSanitizeShadowDOM	DocumentFragment
uponSanitizeShadowNode	Node
afterSanitizeShadowDOM	DocumentFragment
beforeSanitizeAttributes	Element
afterSanitizeAttributes	Element
uponSanitizeElement	Node
uponSanitizeAttribute	Element

To make this as type-safe as possible internally, I've changed the hooks to be stored in an object with properties named after each hook rather than just in an object that keys a string to an array of functions. The _executeHooks function now takes in the array of hooks to execute rather than the name of the hook. This allows the "node" and "data" parameters for the hook to have type-checking applied at compile time to ensure that, for example, you don't call _executeHooks with a Node when the hooks you are executing require an Element.

[cure53]

Awesome, thank you!