Update references from master branch to main branch (#750)

.github/workflows/checks.yml

@@ -3,7 +3,7 @@ name: checks
 on:
   push:
     branches:
-      - master
+      - main
     paths-ignore:
       - '**.md'
   pull_request:

.github/workflows/deploy.yml

@@ -3,7 +3,7 @@ name: demo deploy
 on:
   push:
     branches:
-      - master
+      - main
 
 env:
   FLY_API_TOKEN: ${{ secrets.FLY_TOKEN }}

.github/workflows/docker.yml

@@ -3,7 +3,7 @@ name: docker
 on:
   push:
     branches:
-      - master
+      - main
 
 env:
   GO_VERSION: "1.22"