Update and improve documentation for WebAssembly port

doc/src/getting-started-guide.md

@@ -358,25 +358,67 @@ The following resources may be useful for understanding how to develop Erlang or
 * [Programmers Guide](./programmers-guide.md)
 
 
-## Getting Started with AtomVM WebAssembly port.
+## Getting Started with AtomVM WebAssembly port for NodeJS
 
-AtomVM may be run on platforms with NodeJS from the AtomVM.js file (with its companion AtomVM.wasm file).
+AtomVM's WebAssembly port for NodeJS may be run using `node` command and AtomVM.js, AtomVM.worker.js and AtomVM.wasm files.
 
-Currently, these files must be built and installed from source.
+    shell$ node /path/to/AtomVM.js /path/to/myapp.avm
 
-> See the AtomVM [Build Instructions](./build-instructions.md) for instructions about how to build AtomVM WebAssembly port.
+## Getting Started with AtomVM WebAssembly port for browsers
 
-AtomVM may also be run in modern browsers (Safari, Chrome and Chrome-based, Firefox) from the AtomVM.js, AtomVM.worker.js and AtomVM.wasm files.
+AtomVM may also be run in modern browsers (Safari, Chrome and Chrome-based, Firefox) using AtomVM.js, AtomVM.worker.js and AtomVM.wasm files.
 
-Currently, these files must be built and installed from source. They also need to be installed on a web server that send `Cross-Origin-Opener-Policy` and `Cross-Origin-Embedder-Policy` headers as explained in [Mozilla's documentation](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer#security_requirements).
+Please note that these files are different from the NodeJS ones.
 
-AtomVM comes with a toy web server you can use and run with AtomVM built for Generic Unix with:
+Because AtomVM uses SharedArrayBuffer, to be executed by a browser, these files need to be served:
+- on localhost or over HTTPS
+- by a web server that also sends `Cross-Origin-Opener-Policy` and `Cross-Origin-Embedder-Policy` headers. These headers are also called COOP and COEP headers.
+
+These security requirements are documented in [Mozilla's documentation](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer#security_requirements).
+
+### Trying locally from AtomVM source tree
+
+If you compile AtomVM for Unix as well as for Node as explained in the [build instructions](./build-instructions.md), you can use an AtomVM-based toy webserver to serve the WebAssembly examples with:
 
 ```
 ./src/AtomVM examples/emscripten/wasm_webserver.avm
 ```
 
-This web server serves HTML files from `examples/emscripten/` which you can copy to a webserver along with binaries and built files.
+This web server serves HTML files from `examples/emscripten/`. It works without HTTPS because files are served on localhost.
+
+### Using a hosting service with a `_headers` file
+
+You can also host the three files on a hosting service such as Netlify that uses `_headers` files.
+
+The file could have the following content:
+
+```
+/*
+  Cross-Origin-Opener-Policy: same-origin
+  Cross-Origin-Embedder-Policy: require-corp
+```
+
+### Using web server such as Nginx
+
+You can also host the three files on web server such as Nginx or Apache.
+
+The configuration for Nginx would be:
+
+```
+server {
+   add_header Cross-Origin-Opener-Policy "same-origin";
+   add_header Cross-Origin-Embedder-Policy "require-corp";
+   location / {
+       ...
+   }
+}
+```
+
+### Using Javascript service worker trick
+
+If you have no possibility to modify the headers, for example with GitHub pages, you can still get AtomVM to run in the browser using a Javascript service worker trick.
+
+We did successfully use [coi-serviceworker](https://github.com/gzuidhof/coi-serviceworker).
 
 ## Where to go from here