fix: make package esm-only

BREAKING CHANGE: package is now esm-only

* chore(deps-dev): bump postcss from 8.4.29 to 8.4.31

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.29 to 8.4.31.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.4.29...8.4.31)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

* fix #230 : CJS / ESM conflict

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -1,8 +1,13 @@
 {
   "name": "svelte-i18n",
   "version": "3.7.4",
-  "main": "dist/runtime.cjs.js",
-  "module": "dist/runtime.esm.js",
+  "type": "module",
+  "main": "dist/runtime.js",
+  "exports": {
+    "types": "./dist/runtime.d.ts",
+    "import": "./dist/runtime.js",
+    "require": "./dist/runtime.cjs"
+  },
   "types": "dist/runtime.d.ts",
   "bin": {
     "svelte-i18n": "dist/cli.js"
@@ -92,7 +97,7 @@
     "deepmerge": "^4.2.2",
     "esbuild": "^0.19.2",
     "estree-walker": "^2",
-    "intl-messageformat": "^9.13.0",
+    "intl-messageformat": "^10.5.3",
     "sade": "^1.8.1",
     "tiny-glob": "^0.2.9"
   }