Add Bryan's core code

packages/core/src/interfaces.ts

@@ -0,0 +1,31 @@
+export interface FileDetails {
+    /**
+     * Full path to the file causing the issue.
+     * Note: the agent will translate to the proper repo when posting
+     *       the issue back to the timeline
+     */
+    File: string,
+    Line: number,
+    Column: number
+}
+
+/**
+ * The code to exit an action
+ * Spec: https://github.com/github/dreamlifter/blob/master/docs/actions-model.md#exit-codes
+ */
+export enum ExitCode {
+    /**
+     * A code indicating that the action was successful
+     */
+    Success = 0,
+  
+    /**
+     * A code indicating that the action was a failure
+     */
+    Failure = 1,
+  
+    /**
+     * A code indicating that the action is complete, but neither succeeded nor failed
+     */
+    Neutral = 78
+}