docs: reorder the placeholders alphanumerically

README.md

@@ -240,10 +240,10 @@ Placeholder | Replaced with
 ------------|------------
 `issue_refs` | GitHub issue references to all issues mentioned in the original pull request description seperated by a space, e.g. `#123 #456 korthout/backport-action#789`
 `pull_author` | The username of the original pull request's author, e.g. `korthout`
+`pull_description`| The description (i.e. body) of the original pull request that is backported, e.g. `Summary: This patch was created to..`
 `pull_number` | The number of the original pull request that is backported, e.g. `123`
 `pull_title` | The title of the original pull request that is backported, e.g. `fix: some error`
 `target_branch`| The branchname to which the pull request is backported, e.g. `release-0.23`
-`pull_description`| The description (i.e. body) of the original pull request that is backported, e.g. `Summary: This patch was created to..`
 
 ## Outputs