fix: only emit declaration files from tsc

The TypeScript compiler output was overwriting Babel's output which was
breaking... you guessed it, the fucking `api/test` entrypoint. This
should. fix. it. for. real.

Author: jrolfs

src/tsconfig.json

@@ -5,8 +5,8 @@
   "compilerOptions": {
     "allowJs": true,
     "checkJs": true,
-    "declaration": true,
-    "noEmit": false,
+    "emitDeclarationOnly": true,
+    "declarationMap": true,
     "outDir": "../dist",
     "rootDir": "."
   }