Allow overriding the command passed to Expo

You may want to call into the command action using a provided command
string rather than what comes from the GitHub Action.

This is useful if you want to write an action that listens for a
specific shortcut (e.g. `#release production`) which then calls the
expo/eas command supported by the official action. Then you benefit from
the nice shortcut, remove the possibility of misconfiguration, while
keeping the official GHA's behaviour like posting builds back to the PR
or responding to the original comment.

src/actions/command.ts

@@ -20,6 +20,7 @@ export function commandInput() {
   return {
     reaction: '+1' as Reaction['content'],
     githubToken: getInput('github-token'),
+    commandOverride: getInput('command-override'),
   };
 }
 
@@ -31,7 +32,13 @@ export async function commandAction(input = commandInput()) {
     return;
   }
 
-  const command = parseCommand(comment);
+  let commandSource = comment;
+  if (input.commandOverride) {
+    info(`Overriding command with: ${input.commandOverride}`);
+    commandSource = input.commandOverride;
+  }
+
+  const command = parseCommand(commandSource);
   if (!command) {
     info("Comment didn't contain a valid expo/eas command");
     return;