build: set skipLibCheck... ts-jest and jest aren't playing nicely

I'm not exactly sure why as `ts-jest` looks to be implementing Jest's
`SyncTransform` type properly.

Author: jrolfs

src/tsconfig.json

@@ -5,9 +5,10 @@
   "compilerOptions": {
     "allowJs": true,
     "checkJs": true,
-    "emitDeclarationOnly": true,
     "declarationMap": true,
+    "emitDeclarationOnly": true,
     "outDir": "../dist",
-    "rootDir": "."
+    "rootDir": ".",
+    "skipLibCheck": true
   }
 }