Enable me to create link buttons

[MarcSkovMadsen]

One missing feature in Panel is a way to create a link button. You have two options

• Button with on_js: Style is built in. But you cannot right click and open link.
• HTML anchor: You have to style but can right click to open link.

I can see that Material UI support a link on a Button via the href property.

Please support this property

Please consider support href property on Panel button too.