add search page

[techieshark]

Fixes #99

See #99 or commits here for changes made, but basically:

• New API endpoint (POST /api/rpc/search_stories BODY = { query: "some string" }) for performing search across story titles and suburb names.
• Elm keeps track of state, updates URL hash and signals through a port to JS when the search screen should be shown
• JS fires a request to the API when the search input field is updated

Todo later:

• cache results so we don't fire same request redundantly
• maybe have a source for smaller images to include in search results
• maybe highlight what matched
• maybe search suburbs too

[more-like-a-puma]

💯 % A++