Adopted WP standard block location

Moved blocks into a multi-block folder structure
Added url-loader for static images
Moved CSS to build dir

build/editor.css

@@ -0,0 +1,9 @@
+/**
+ * The following styles get applied inside the editor only.
+ *
+ * Replace them with your own styles or remove the file completely.
+ */
+
+.wp-block-wp-strava-activity {
+	border: 1px dotted #f00;
+}