add gravatar utils

packages/app/src/utils/gravatar.ts

@@ -0,0 +1,8 @@
+import md5 from 'md5';
+
+export const GRAVATAR_DEFAULT = 'https://gravatar.com/avatar/00000000000000000000000000000000?s=24';
+
+export const generateGravatarSrc = (email?: string): string => {
+  const hash = md5((email ?? '').trim().toLowerCase());
+  return `https://gravatar.com/avatar/${hash}`;
+};