fix ci badge link

Author: kevinlang

.github/workflows/main.yml renamed to .github/workflows/ci.yml

@@ -1,4 +1,4 @@
-name: Main Workflow
+name: CI
 on: [push, pull_request]
 jobs:
   test-elixir:

README.md

@@ -1,6 +1,6 @@
 # Ecto SQLite3 Adapter
 
-[![Build Status](https://github.com/elixir-sqlite/ecto_sqlite3/workflows/main/badge.svg)](https://github.com/elixir-sqlite/ecto_sqlite3/actions)
+[![Build Status](https://github.com/elixir-sqlite/ecto_sqlite3/workflows/CI/badge.svg)](https://github.com/elixir-sqlite/ecto_sqlite3/actions)
 
 An Ecto SQLite3 Adapter.