Improve developer documentation

DEVELOP.md

@@ -31,21 +31,16 @@
 ## Manual installation
 
 - Clone the repository.
-- From the Google Chrome extensions settings page:
+- Build the code using commands below.
+- From the browser extensions settings page:
   - Enable developer mode.
-  - Load the repository folder as an unpacked extension.
+  - Load one of the package folders as an unpacked extension.
+    - `package/chrome/` for Google Chrome, Chromium, Vivaldi, and similar browser.
+    - `package/webextension/` for Firefox, and other browsers.
 
 
 
-## Debugging
-
-- From the Google Chrome extensions settings page:
-  - Inspect the Talkie background page view to see console output.
-  - Optionally add breakpoints in the source code.
-
-
-
-## Development
+## Building
 
 ```bash
 # Go to the directory where you cloned the repository.
@@ -54,12 +49,22 @@ cd talkie
 # Install local development tools.
 npm install
 
-# Fix any warnings and errors before committing.
-npm run --silent test
+# Do a clean build.
+npm run --silent rebuild
 ```
 
 
 
+## Debugging
+
+- From the browser extensions settings page:
+  - Enable developer mode.
+  - Inspect the Talkie background page view to see console output.
+- You can also inspect the popup and options pages separately.
+- Optionally add breakpoints in the source code.
+
+
+
 ## Translations
 
 In order to offer Talkie in as many languages as possible, translations are automated. It is still possible — and preferred — to add overrides with human translations.
@@ -112,8 +117,21 @@ git flow feature start <feature-name>
 npm run --silent watch:background
 npm run --silent watch:popup
 npm run --silent watch:options
+npm run --silent watch:chrome
+npm run --silent watch:webextension
 
 # Code your feature and add the files.
+# Manually reload and test the code in the browser.
+# Manually test all Talkie features:
+#   - The Talkie button
+#   - Shortcut keys
+#   - Options page
+#   - Language detection in more than one language
+#   - Any feature change you may have made
+# in the supported browsers:
+#   - Google Chrome
+#   - Firefox
+#   - Preferably other browsers as well.
 
 # Make sure the code builds.
 npm run --silent rebuild