fix: generate valid javascript modules in build (#1080)

Before this change snabbdom could only be consumed by bundlers like webpack.
Now we add the `.js` extension to the build outputs so browsers can import the modules directly as well.
ISSUES FIXED: #963

package-lock.json

@@ -32,6 +32,7 @@
         "prettier": "^3.0.3",
         "release-it": "^16.2.1",
         "serve": "^14.2.1",
+        "ts-add-js-extension": "^1.6.0",
         "typescript": "5.2.2"
       },
       "engines": {
@@ -12722,6 +12723,18 @@
         "node": "*"
       }
     },
+    "node_modules/ts-add-js-extension": {
+      "version": "1.6.0",
+      "resolved": "https://registry.npmjs.org/ts-add-js-extension/-/ts-add-js-extension-1.6.0.tgz",
+      "integrity": "sha512-vJSCfL0YEn0tPxJKSOgMEjxPoKnqLaW+stSLEtpY974/GkgEVukc0O7Q4ryAGbvEzP1WYVW/w563TO3uvFFbqw==",
+      "dev": true,
+      "dependencies": {
+        "typescript": "^5.2.2"
+      },
+      "bin": {
+        "ts-add-js-extension": "build/cjs/bin.js"
+      }
+    },
     "node_modules/ts-api-utils": {
       "version": "1.0.3",
       "resolved": "https://registry.npmjs.org/ts-api-utils/-/ts-api-utils-1.0.3.tgz",

package.json

@@ -31,7 +31,7 @@
   "types": "build/index.d.ts",
   "sideEffects": false,
   "scripts": {
-    "build": "tsc",
+    "build": "tsc && ts-add-js-extension --dir=build",
     "examples": "serve .",
     "format": "prettier --write .",
     "prepare": "husky install",
@@ -65,6 +65,7 @@
     "prettier": "^3.0.3",
     "release-it": "^16.2.1",
     "serve": "^14.2.1",
+    "ts-add-js-extension": "^1.6.0",
     "typescript": "5.2.2"
   },
   "prettier": {