Pr/avatar (#319)

* feat: add avatar api
close #310

* chore: add description line

* fix: typo

* chore: reformat the json string to make it more readable and fix few bad indents

* fix: minimum go version

* feat: upload to Micro's CDN

* chore: delete redundant blank line

* chore: update README.md

avatar/publicapi.json

@@ -0,0 +1,6 @@
+{
+  "name": "avatar",
+  "icon": "🤳🏻",
+  "category": "for fun",
+  "display_name": "Avatar"
+}