Add an OSM signup prompt to the reporting-method and app pages (#133)

* Point new contributors at OSM signup before they pick a reporting method

Both reporting paths write to OpenStreetMap, but the only signup link lived in
step 1 of the web instructions, so anyone landing on /report or /app had no signal
they needed an account until they hit the login wall.

Adds a callout on the reporting-method page and a line under the app download
CTA, both linking to openstreetmap.org/user/new. Closes #86.

* Move the OSM note into the hero and link the About page

* Update ReportChoose.vue

webapp/src/views/DeflockApp.vue

@@ -61,6 +61,11 @@
                   <v-icon icon="mdi-open-in-new" size="small" class="ml-1" />
                 </v-btn>
               </div>
+              <p class="hero-note">
+                Submitting or editing map data requires signing up for a free
+                <a href="https://wiki.openstreetmap.org/wiki/About_OpenStreetMap" target="_blank">OpenStreetMap</a> account.
+                You can <a href="https://www.openstreetmap.org/user/new" target="_blank">sign up here</a> with just an email address.
+              </p>
             </div>
           </v-col>
           <v-col cols="12" md="6" class="hero-image">
@@ -821,6 +826,18 @@ const visibleScreenshots = computed(() =>
   opacity: 0.7;
 }
 
+.hero-note {
+  margin-top: 24px;
+  font-size: 0.95rem;
+  opacity: 0.85;
+}
+
+/* The hero sits on a dark gradient, so the default link blue is unreadable. */
+.hero-note a {
+  color: inherit;
+  text-decoration: underline;
+}
+
 /* Responsive Design */
 @media (max-width: 960px) {
   .hero-title {

webapp/src/views/ReportChoose.vue

@@ -10,6 +10,15 @@
       </v-col>
     </v-row>
 
+    <v-row justify="center" class="mb-4">
+      <v-col cols="12" md="8">
+        <v-alert variant="tonal" type="info" density="comfortable">
+          DeFlock uses <b><a href="https://wiki.openstreetmap.org/wiki/About_OpenStreetMap" target="_blank">OpenStreetMap</a></b> data;
+          you'll need to <a href="https://www.openstreetmap.org/user/new" target="_blank">create an OpenStreetMap account</a> to make submissions.
+        </v-alert>
+      </v-col>
+    </v-row>
+
     <!-- ALPR Identification Warning -->
     <v-row justify="center" class="mb-8">
       <v-col cols="12" class="text-center">
@@ -120,4 +129,4 @@ import DefaultLayout from '@/layouts/DefaultLayout.vue';
   position: relative;
   z-index: 1;
 }
-</style>
+</style>