separated type definitions and util functions

tsconfig.eslint.json

@@ -0,0 +1,11 @@
+// Special typescript project file, used by eslint only.
+{
+    "extends": "./tsconfig.json",
+    "include": [
+        // repeated from base config's "include" setting
+        "src",
+
+        // these are the eslint-only inclusions
+        ".eslintrc.json",
+    ]
+}