Merge branch 'improve-styling' into 'master'

Apply symbol names to widget paths, add styles

See merge request Librem5/squeekboard!148

data/style.css

@@ -17,3 +17,11 @@
     background: #1c71d8;
     border-color: #3584e4;
 }
+
+#Return {
+    background: #6480ff
+}
+
+#Shift_L {
+    background: #363438
+}