Export wasm light client's IndexedDB to a JSON file

[pmespresso]

It's super annoying during development when the client goes Idle and we need to restart from block 0.

Something like this supposedly works in electron and could work from a browser as well with some tweaks to ditch the node dependencies. But I think we just need to sync with the electron app, then run this script, and find a way to import it from browser. From what I've read, anything over 5MB will be problematic but I'm more than happy to try regardless

snippet from https://github.com/Polarisation/indexeddb-export-import

// export indexed db to json string
var Dexie = require("Dexie");
var IDBExportImport = require("indexeddb-export-import")

var db = new Dexie("Kusama CC3", 1);
db.version(1).stores({
	things : "id++, thing_name, thing_description",
});
db.open().then(function() {
	var idb_db = db.backendDB(); // get native IDBDatabase object from Dexie wrapper

	// export to JSON, clear database, and import from JSON
	IDBExportImport.exportToJsonString(idb_db, function(err, jsonString) {
		if(err)
			console.error(err);
		else {
			console.log("Exported as JSON: " + jsonString);
			IDBExportImport.clearDatabase(idb_db, function(err) {
				if(!err) // cleared data successfully
					IDBExportImport.importFromJsonString(idb_db, jsonString, function(err) {
						if (!err)
							console.log("Imported data successfully");
					});
			});
		}
	});
}).catch(function(e) {
	console.error("Could not connect. " + e);
});