[FEATURE] Support encapsulation within Shadow DOM

[niklaushug]

Feature description

1. Append calendar to Shadow DOM if needed.
2. Do not hide calendar if calendar or input (if inputMode: true) is clicked.

Use case
We think vanilla-calendar-pro is a great fit for our Lit-based design system. All our components are encapsulated in custom elements and use Shadow DOM.

Proposed solution
Features 1 and 2 are addressed in my Fork.

Consideration
To check if more code has to be changed to support Shadow DOM I searched for 'document':

3. Method queryAndMemoize should query its RootNode if needed. Only querying 'document' may fail. The method name seems to have a typo (missing 'r').
4. May you want execute the conditionals on line 35 and 36 only if the calendar resides inside a Shadow DOM.

Sample
Commit Add webcomponent sample. shows a minimalistic web component with a calendar. May toggle settings inputMode.

[uvarov-frontend]

Thank you, a good idea.