Testing support

[lucaslenz]

Hello,

first of all thank you for you library! I really do enjoy using it!

However it is currently not possible to unit test components that use this library as it uses DOMRect which is currently not supported by jsdom or happy-dom. There is an open ticket for Geomtry support in jsdom and I just issued a ticket for happy-dom.

I know that this may not be the scope of this library but it would be an enhancement to be able to use this package in testing environments. There are basically two options to add testing support I am aware of:

1. Wait for happy-dom/jsdom to implement the geometry spec
2. Use a implementation that is compliant to happy-dom/jsdom.

For me personally, this is a blocker as I cannot use the library without testing support.

I am willing to further support investigation and implementation on this!