feat(search): add game search page (#50)

Add /search to find games by name on IGDB.
A game in the library opens its game page. Other hits open a
detail view with an Add button. The query stays in the URL.
To fit the new nav icon on 360 px phones, the header padding is
smaller and the points chip hides while the Questions icon shows.

src/components/AppHeader.test.jsx

@@ -55,6 +55,12 @@ describe('AppHeader', () => {
         expect(screen.getByTitle('NAV.FOLLOWING').getAttribute('href')).toBe('/following');
     });
 
+    it('links to the game search when logged in', () => {
+        loggedInAs({role: 'USER', activeRole: 'USER'});
+
+        expect(screen.getByTitle('NAV.SEARCH').getAttribute('href')).toBe('/search');
+    });
+
     it('links to the community stats when logged in', () => {
         loggedInAs({role: 'USER', activeRole: 'USER'});