Merge pull request #3 from dawitnida/fix/validate-action-readme

Added validate command instruction.

validate/README.md

@@ -0,0 +1,28 @@
+# Packer Validate Action
+
+Runs `packer validate *.json` on pull request to validate the syntax and configuration of a template file in a directory
+If the validation fails, it will print out error as pull request comment.
+Check out the [packer validate command][packer-validate-doc] for further reference. 
+
+## Usage
+
+```
+workflow "Packer" {
+  resolves = "packer-validate"
+  on = "pull_request"
+}
+
+action "filter-open-synced-pr" {
+  uses = "actions/bin/filter@master"
+  args = "action 'opened|synchronize'"
+}
+
+action "packer-validate" {
+  uses = "dawitnida/packer-github-actions/validate@master"
+  needs = "filter-open-synced-pr"
+  secrets = ["GITHUB_TOKEN"]
+  args = "*.json"
+}
+```
+
+[packer-validate-doc]:  <https://www.packer.io/docs/commands/validate.html>