fix: missing examples in README (#192)

Author: gabrielmfern

readme.md

@@ -1,11 +1,16 @@
 # resend-examples
 
 - [Attachments](/with-attachments/)
+  - [Attachments with Buffer content](/with-attachments-content/)
+  - [iCal](/with-ical/)
 - Custom Headers
   - [Prevent thread on Gmail](/with-prevent-thread-on-gmail/)
   - [Unsubscribe URL header](/with-unsubscribe-url-header/)
 - [Domains methods](/with-domains/)
 - [Next.js Auth](/with-nextauth/)
 - [React Email](/with-react-email/)
+  - [Express and React Email](/with-express-react-email/)
+- [Python asyncio](/with-python-asyncio/)
 - [Sinatra](/with-sinatra/)
-- [Webhooks](/with-webhooks/)
+- [Webhooks](/with-webhooks/)
+  - [Webhooks with Python Flask](/with-webhooks-python-flask/)