feat: added typescript definitions (#68)

Co-authored-by: James Mortemore <[email protected]>

Author: ltphen

.gitignore

@@ -6,3 +6,4 @@ npm-debug.log
 typings*
 .sync
 .vscode
+.idea

index.d.ts

@@ -0,0 +1,5 @@
+import {GraphQLSchema} from "graphql";
+
+export function constraintDirective () : (schema: GraphQLSchema) => GraphQLSchema;
+
+export const constraintDirectiveTypeDefs: string

package.json

@@ -3,6 +3,7 @@
   "version": "2.1.1",
   "description": "Validate GraphQL fields",
   "main": "index.js",
+  "types": "index.d.ts",
   "scripts": {
     "test": "standard && nyc --reporter=html --reporter=text --reporter=lcov mocha test/**/*.test.js"
   },