fix: support TS resolution for .mjs

Signed-off-by: Alex Regan <alex.regan@alexregan.com>

See here for explanation of problem and solution:

https://stackoverflow.com/questions/72457791/typescript-packages-that-ship-with-mjs-and-d-ts-but-without-d-mts-how-to-i

package.json

@@ -6,6 +6,7 @@
   "exports": {
     ".": {
       "require": "./index.js",
+      "types": "./index.d.ts",
       "import": "./index.mjs"
     },
     "./aws": "./lib/aws/index.js",