Fix #4 Update @actions/core

See here for further details:
https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands

node_modules/@actions/core/lib/utils.js

@@ -0,0 +1,19 @@
+"use strict";
+// We use any as a valid input type
+/* eslint-disable @typescript-eslint/no-explicit-any */
+Object.defineProperty(exports, "__esModule", { value: true });
+/**
+ * Sanitizes an input into a string so it can be passed into issueCommand safely
+ * @param input input to sanitize into a string
+ */
+function toCommandValue(input) {
+    if (input === null || input === undefined) {
+        return '';
+    }
+    else if (typeof input === 'string' || input instanceof String) {
+        return input;
+    }
+    return JSON.stringify(input);
+}
+exports.toCommandValue = toCommandValue;
+//# sourceMappingURL=utils.js.map