fix: Correct the PortalProvider's getContainer typings

[alexasselin008]

Closes

There was a small issue in the getContainer's typings.

There is the following code

    <PortalContext.Provider value={{getContainer: getContainer === null ? undefined : getContainer ?? ctxGetContainer}}>

Which means getContainer is intented to be null sometimes. There is a comment that also imply this:

Can clear the context by passing null.

But at the moment, getContainer does not accept the null value.

before:

(() => HTMLElement | null) | undefined

now:

(() => HTMLElement | null) | null | undefined

[alexasselin008]

The Ci gives 43 lint error, not too sure what is happening here. They seem unrelated to my changes

[snowystinger]

Those are lint warnings and you can ignore them. It failed on the tsc step