Update README

ucan-wasm/README.md

@@ -1,11 +1,28 @@
 ### Build
 
+The build command output for `browser`, `node`, `deno`, and `workerd` targets to `ucan-wasm/lib`.
+
 ```
-wasm-pack build --target web
+npm run build
 ```
 
 ### Test
 
+The test command tests `node` and browser environments including `chromium`, `firefox`, and `webkit`
+using headless browsers.
+
 ```
 npm run test
 ```
+
+Testing can also be run for `node` only.
+
+```
+npm run test:node
+```
+
+The test commands runs `build` to ensure all targets are available for testing.
+
+### Reporting
+
+Test runs output test results and coverage as JSON artifacts to `ucan-wasm/tests/report`.