Add node modules and new code for release (#57)

Co-authored-by: taakleton <taakleton@users.noreply.github.com>

node_modules/istanbul-lib-report/lib/report-base.js

@@ -0,0 +1,16 @@
+'use strict';
+
+// TODO: switch to class private field when targetting node.js 12
+const _summarizer = Symbol('ReportBase.#summarizer');
+
+class ReportBase {
+    constructor(opts = {}) {
+        this[_summarizer] = opts.summarizer;
+    }
+
+    execute(context) {
+        context.getTree(this[_summarizer]).visit(this, context);
+    }
+}
+
+module.exports = ReportBase;