Add an example to read/write indexeddb

[CaledoniaProject]

Can you add an example on IndexedDB? e.g read/write/loop through keys

[niloc132]

I suggest starting with a resource for how to use IndexedDB in general in the browser - the API should be the same, but the syntax will just be java instead of JS. For example, see https://developer.mozilla.org/en-US/docs/Web/API/IndexedDB_API.