Add support for deleting properties

[luisherranz]

What

Add support for deleting properties like delete store.a.

Why

Because it's another type of mutation that can be applied to plain JS objects, so it should be supported.

How

Add the deleteProperty handler.

I branched this PR on top of luisherranz/deepsignal#20, so we should wait until that one is merged to merge this one.

[github-actions]

Size Change: +279 B (+5%) 🔍

Total Size: 5.75 kB

Filename	Size	Change
packages/deepsignal/core/dist/deepsignal-core.js	939 B	+49 B (+6%)	🔍
packages/deepsignal/core/dist/deepsignal-core.mjs	923 B	+43 B (+5%)	🔍
packages/deepsignal/dist/deepsignal.js	976 B	+46 B (+5%)	🔍
packages/deepsignal/dist/deepsignal.mjs	970 B	+47 B (+5%)	🔍
packages/deepsignal/react/dist/deepsignal-react.js	975 B	+46 B (+5%)	🔍
packages/deepsignal/react/dist/deepsignal-react.mjs	970 B	+48 B (+5%)	🔍

_{compressed-size-action}

[DAreRodz]

Nice addition 👍