Add package-lock.json back

Due to some recent problems with type generation w.r.t differing
versions of dependencies, we're putting the `package-lock.json` back in.

At least according to
npm/npm#17979 (comment),
everything should be working as expected with npm >=5.4.2

Author: dfreedm

.gitignore

@@ -11,5 +11,4 @@ dist
 
 # misc
 .DS_Store
-npm-debug.log
-package-lock.json
+npm-debug.log