Update AWS SAM template

Author: Charoite Lee

package-sam.yml

@@ -5,10 +5,10 @@ Resources:
         Type: AWS::Serverless::LayerVersion
         Properties:
             LayerName: canvas-nodejs
-            Description: canvas@2.8.0
-            ContentUri: s3://lambda-layer-charoitel/canvas-nodejs_v2.8.1.zip
+            Description: canvas@<CANVAS_VERSION>
+            ContentUri: s3://<S3_BUCKET_NAME>/canvas-nodejs_v<CANVAS_VERSION>.zip
             CompatibleRuntimes:
-                - nodejs14.x
+                - nodejs<NODEJS_RUNTIME_VERSION>
             RetentionPolicy: Retain
             LicenseInfo: MIT