fix: show the date property value in preview (#880)

[JimMorrison723]

Problem: As mentioned in #880, when the property type is date, the devtools just shows Date() instaed of showing the Date value as well.

I believe this is good enough for an MVP, just to show the date. (i would live to update the tests for this, but i believe there is none for this)

I believe we could further improve the UX and DX later on, by:

• Updating the demo app, so there would be a page, with all kinds of inputs, to test it out while developing the devtools
• Instead of just showing the property in an editable, it would be nice if a little icon would show up telling us it is indeed a Date type property. Just looking at the current solution, one might think it's a simple string (like in the vue devtools)
• I feel like devtool panel components should be refactord to be OnPush components. It's clear, that it has Inputs/Outputs, so tweaking it a little so changes are always immutable we could improve perf

Let me know what you think. I might create an issue for these, so we can improve this project in small steps.

[mgechev]

Thanks for the PR! We're in a process of moving DevTools to the Angular monorepo. Would you follow up with the change there once we merge https://github.com/angular/angular/pull/43473?

[JimMorrison723]

Yes, of course!