Use actions/checkoutv@3 in examples (#692)

change actions/checkout version

README.md

@@ -92,7 +92,7 @@ jobs:
 
     steps:
       - name: Check out Git repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       # Install your linters here
 
@@ -130,7 +130,7 @@ jobs:
 
     steps:
       - name: Check out Git repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Set up Node.js
         uses: actions/setup-node@v1
@@ -172,7 +172,7 @@ jobs:
 
     steps:
       - name: Check out Git repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Set up PHP
         uses: shivammathur/setup-php@v2
@@ -211,7 +211,7 @@ jobs:
 
     steps:
       - name: Check out Git repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Set up PHP
         uses: shivammathur/setup-php@v2
@@ -253,7 +253,7 @@ jobs:
 
     steps:
       - name: Check out Git repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Set up Python
         uses: actions/setup-python@v1
@@ -292,7 +292,7 @@ jobs:
 
     steps:
       - name: Check out Git repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Install ClangFormat
         run: sudo apt-get install -y clang-format
@@ -325,7 +325,7 @@ jobs:
 
     steps:
       - name: Check out Git repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Set up .NET
         uses: actions/setup-dotnet@v1
@@ -360,7 +360,7 @@ jobs:
 
     steps:
       - name: Check out Git repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Set up Python
         uses: actions/setup-python@v1