feat: add TypeScript definitions and update package exports

Author: mceachen

index.d.ts

@@ -0,0 +1,5 @@
+import { Knex } from "knex";
+
+declare class Client_PhotoStructureSQLite extends Knex.Client {}
+
+export = Client_PhotoStructureSQLite;

package.json

@@ -3,12 +3,17 @@
   "version": "0.1.0",
   "description": "Knex.js dialect for @photostructure/sqlite",
   "main": "./index.js",
+  "types": "./index.d.ts",
   "exports": {
-    ".": "./index.js",
+    ".": {
+      "types": "./index.d.ts",
+      "default": "./index.js"
+    },
     "./package.json": "./package.json"
   },
   "files": [
     "index.js",
+    "index.d.ts",
     "LICENSE",
     "README.md"
   ],