fix(editor): always use random hex colors

chance.color() can output all valid CSS
values for colors, including rgba() syntax and predefined color
names. Due to the usage of hex2rgb and other methods, this can
break the editor. This commit ensures that all randomly generated
colors are specified in hex format.

Signed-off-by: Erik Michelson <github@erik.michelson.eu>

lib/letter-avatars.js

@@ -8,6 +8,7 @@ const config = require('./config')
 exports.generateAvatar = function (name) {
   // use darker colors for better contrast
   const color = new Chance(name).color({
+    format: 'hex',
     max_red: 150,
     max_green: 150,
     max_blue: 150