Add dependency-graph-continue-on-failure input param

- Translate to env var for init-script support
- Use when deciding whether to log or rethrow errors
- Add a custom error type to trigger failure in post action

src/errors.ts

@@ -0,0 +1,11 @@
+export class PostActionJobFailure extends Error {
+    constructor(error: unknown) {
+        if (error instanceof Error) {
+            super(error.message)
+            this.name = error.name
+            this.stack = error.stack
+        } else {
+            super(String(error))
+        }
+    }
+}