ip addresses: add ip address show page.

* Add IP address show page at /ip_addresses/1.2.3.4.
* Add "Details", "Ban IP", "Ban User" options to the /ip_addresses listing.

app/helpers/ip_addresses_helper.rb

@@ -0,0 +1,11 @@
+module IpAddressesHelper
+  def embedded_google_map(location, width, height, api_key: Danbooru.config.google_maps_api_key)
+    tag.iframe(
+      width: width,
+      height: height,
+      frameborder: 0,
+      allowfullscreen: true,
+      src: "https://www.google.com/maps/embed/v1/search?q=#{location}&key=#{api_key}"
+    )
+  end
+end