Chore: Update default branch name to "main"

Author: lumaxis

.github/workflows/ci.yml

@@ -5,9 +5,9 @@ name: VS Code Extension CI
 
 on:
   push:
-    branches: [ master ]
+    branches: [ main ]
   pull_request:
-    branches: [ master ]
+    branches: [ main ]
 
 jobs:
   build:

README.md

@@ -1,7 +1,7 @@
 <p align="center">
   <img
     width="100"
-    src="https://raw.githubusercontent.com/lumaxis/snippet-copy/master/images/icon.png"
+    src="https://raw.githubusercontent.com/lumaxis/snippet-copy/main/images/icon.png"
     alt="Snippet Copy"
   />
 	<h1 align="center">Snippet Copy</h1>