New "browse" UI

Also, separated out browse, ?meta, and ?module request handlers.

Fixes #82

modules/client/browse/PackageInfo.js

@@ -0,0 +1,11 @@
+import React, { createContext, useContext } from 'react';
+
+const Context = createContext();
+
+export function PackageInfoProvider({ children, ...rest }) {
+  return <Context.Provider children={children} value={rest} />;
+}
+
+export function usePackageInfo() {
+  return useContext(Context);
+}