Add destroy method to TooltipView

[fkling]

Other components that extend the editor's DOM have a destroy method that allows them to clean up any resources they created (e.g. PluginValue, Panel). I've been missing such a method for the TooltipView as well. Although I found a workaround by using MutationObserver like so

    public mount(): void {
        if (this.dom.parentElement) {
            const observer = new MutationObserver(mutations => {
                for (const mutation of mutations) {
                    if (mutation.type === 'childList' && Array.from(mutation.removedNodes).includes(this.dom)) {
                        // clean up here
                        observer.disconnect()
                        return
                    }
                }
            })
            observer.observe(this.dom.parentElement, { childList: true })
        }
    }

I think it would be nice to have such a method for simplicity and consistency.

Note: I extended one of the hover tests but I wasn't able to actually run web tests via npm run test. I got an error that the @codemirror/view dependency doesn't exist (which makes sense) but I don't know what the necessary steps are to get the tests running.

[marijnh]

This is a good idea. Thanks for the patch!

[fkling]

Thank you for accepting it!