fix(types): updates package.json for type resolution (#55)

The `types` field was missing and `exports["."].types` fields pointed to
the legacy filename still. This PR updates both to point at the proper
file in the distributed files.

package.json

@@ -4,11 +4,12 @@
   "description": "A micro-package to convert style objects to css strings.  Inspired by extensive usage of styled-components.",
   "main": "./dist/index.cjs",
   "module": "./dist/index.mjs",
+  "types": "./dist/index.d.ts",
   "exports": {
     ".": {
       "require": "./dist/index.cjs",
       "import": "./dist/index.mjs",
-      "types": "./dist/main.d.ts"
+      "types": "./dist/index.d.ts"
     },
     "./parsers": {
       "require": "./dist/parsers/index.cjs",