Fix branch name in workflows

Author: bash

.github/workflows/build.yml

@@ -3,11 +3,11 @@ name: Build
 on:
   push:
     branches:
-      - master
+      - main
 
   pull_request:
     branches:
-      - master
+      - main
 
 jobs:
   build:

.github/workflows/docs.yml

@@ -3,21 +3,21 @@ name: Build Documentation
 on:
   pull_request:
     branches:
-      - master
+      - main
   push:
     branches:
-      - master
+      - main
 
 jobs:
   build:
     runs-on: ubuntu-latest
-    
+
     steps:
     - uses: actions/checkout@v1
     - name: Setup mdBook
       uses: peaceiris/actions-mdbook@v1
       with:
-        mdbook-version: '0.4.0' 
+        mdbook-version: '0.4.0'
     - name: Build Documentation
       run: mdbook build
       working-directory: ./documentation