Allow erasable syntax only (#70)

Author: kevgo

tsconfig.json

@@ -77,7 +77,7 @@
     // "isolatedModules": true,                          /* Ensure that each file can be safely transpiled without relying on other imports. */
     // "verbatimModuleSyntax": true,                     /* Do not transform or elide any imports or exports not marked as type-only, ensuring they are written in the output file's format based on the 'module' setting. */
     // "isolatedDeclarations": true,                     /* Require sufficient annotation on exports so other tools can trivially generate declaration files. */
-    // "erasableSyntaxOnly": true,                       /* Do not allow runtime constructs that are not part of ECMAScript. */
+    "erasableSyntaxOnly": true, /* Do not allow runtime constructs that are not part of ECMAScript. */
     // "allowSyntheticDefaultImports": true,             /* Allow 'import x from y' when a module doesn't have a default export. */
     "esModuleInterop": false, /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */
     // "preserveSymlinks": true,                         /* Disable resolving symlinks to their realpath. This correlates to the same flag in node. */