Refactor explorer config into useKnockoutExplorer hook (#397)

Co-authored-by: Steve Faulkner <stfaul@microsoft.com>

src/hooks/useConfig.ts

@@ -0,0 +1,14 @@
+import { useEffect, useState } from "react";
+import { ConfigContext, initializeConfiguration } from "../ConfigContext";
+
+// This hook initializes global configuration from a config.json file that is injected at deploy time
+// This allows the same main Data Explorer build to be exactly the same in all clouds/platforms,
+// but override some of the configuration as nesssary
+export function useConfig(): Readonly<ConfigContext> {
+  const [state, setState] = useState<ConfigContext>();
+
+  useEffect(() => {
+    initializeConfiguration().then((response) => setState(response));
+  }, []);
+  return state;
+}