build: replace tsup with tsdown

Author: OliverDudgeon

package.json

@@ -3,26 +3,34 @@
   "version": "5.0.0",
   "type": "module",
   "description": "MUI theme used on Squonk products",
-  "module": "./src/index.ts",
-  "typings": "./src/index.ts",
-  "publishConfig": {
-    "main": "./dist/index.cjs",
-    "module": "./dist/index.js",
-    "typings": "./dist/index.d.ts"
-  },
   "sideEffects": false,
   "repository": "github:InformaticsMatters/squonk-react-mui-theme",
   "license": "Apache-2.0",
   "private": false,
   "homepage": "https://github.com/InformaticsMatters/squonk-react-mui-theme/",
+  "main": "./dist/index.cjs",
+  "module": "./dist/index.js",
+  "types": "./dist/index.d.cts",
+  "exports": {
+    ".": "./src/index.ts",
+    "./package.json": "./package.json"
+  },
+  "publishConfig": {
+    "exports": {
+      ".": {
+        "require": "./dist/index.cjs",
+        "import": "./dist/index.js"
+      },
+      "./package.json": "./package.json"
+    }
+  },
   "scripts": {
     "prepare": "husky install",
-    "build": "tsup",
-    "start": "tsup --watch",
+    "build": "tsdown",
+    "start": "tsdown --watch",
     "tsc": "tsc --pretty --noEmit",
     "lint": "eslint --cache --max-warnings=0",
-    "format": "eslint --fix --cache --max-warnings=0",
-    "release": "semantic-release"
+    "format": "eslint --fix --cache --max-warnings=0"
   },
   "peerDependencies": {
     "@mui/material": ">5"
@@ -39,7 +47,7 @@
     "lint-staged": "15.5.0",
     "semantic-release": "24.2.3",
     "tslib": "2.8.1",
-    "tsup": "8.4.0",
+    "tsdown": "0.18.3",
     "typescript": "5.8.2"
   },
   "lint-staged": {