fix(wasm): use .mjs extension for ES modules compatibility

- Rename generated .js to .mjs to avoid needing type:module in pkg/package.json
- Update imports to use .mjs extension
- Add LICENSE file to wasm directory
- Simplifies the build process and removes complex post-build scripts

Author: jp-knj

wasm/LICENSE

@@ -0,0 +1,22 @@
+(The MIT License)
+
+Copyright (c) 2022 Titus Wormer <[email protected]>
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+'Software'), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

wasm/lib/index.mjs

@@ -7,7 +7,7 @@ let wasmModule = null;
 
 async function loadWasmModule() {
   if (!wasmModule) {
-    wasmModule = await import('../pkg/markdown_rs_wasm.js');
+    wasmModule = await import('../pkg/markdown_rs_wasm.mjs');
   }
   return wasmModule;
 }

wasm/package.json

@@ -10,7 +10,7 @@
     "README.md"
   ],
   "scripts": {
-    "build": "wasm-pack build --target web --out-dir pkg",
+    "build": "wasm-pack build --target web --out-dir pkg && mv pkg/markdown_rs_wasm.js pkg/markdown_rs_wasm.mjs",
     "test": "node --test test/index.test.mjs",
     "example:basic": "node examples/basic.mjs",
     "example:options": "node examples/with-options.mjs"