Add core.isDebug() to check whether actions_step_debug is on or not. (#278)

src/core.ts

@@ -102,6 +102,13 @@ export function setFailed(message: string): void {
 // Logging Commands
 //-----------------------------------------------------------------------
 
+/**
+ * Gets whether Actions Step Debug is on or not
+ */
+export function isDebug(): boolean {
+  return process.env['RUNNER_DEBUG'] === '1'
+}
+
 /**
  * Writes debug message to user log
  * @param message debug message