fix(package): add exports map to package.json (#77)

Fixes #76

package.json

@@ -4,10 +4,24 @@
   "license": "MIT",
   "description": "Detect if an element is in the viewport using the Intersection Observer API",
   "author": "Eric Liu (https://github.com/metonym)",
+  "type": "module",
   "svelte": "./src/index.js",
   "main": "./src/index.js",
   "types": "./src/index.d.ts",
-  "type": "module",
+  "exports": {
+    ".": {
+      "types": "./types/index.d.ts",
+      "svelte": "./src/index.js"
+    },
+    "./src/*.svelte": {
+      "types": "./src/*.svelte.d.ts",
+      "import": "./src/*.svelte"
+    },
+    "./src/*": {
+      "types": "./src/*.d.ts",
+      "import": "./src/*.js"
+    }
+  },
   "scripts": {
     "dev": "rollup -cw",
     "build": "rollup -c",