qmk docs: Add flag to open in browser (qmk#13788)

* `qmk docs`: Add flag to open in browser

* Add docs

docs/cli_commands.md

@@ -349,11 +349,12 @@ qmk cformat -b branch_name
 ## `qmk docs`
 
 This command starts a local HTTP server which you can use for browsing or improving the docs. Default port is 8936.
+Use the `-b`/`--browser` flag to automatically open the local webserver in your default browser.
 
 **Usage**:
 
 ```
-qmk docs [-p PORT]
+qmk docs [-b] [-p PORT]
 ```
 
 ## `qmk generate-docs`

lib/python/qmk/cli/docs.py

@@ -2,21 +2,26 @@
 """
 import http.server
 import os
+import webbrowser
 
 from milc import cli
 
 
 @cli.argument('-p', '--port', default=8936, type=int, help='Port number to use.')
+@cli.argument('-b', '--browser', action='store_true', help='Open the docs in the default browser.')
 @cli.subcommand('Run a local webserver for QMK documentation.', hidden=False if cli.config.user.developer else True)
 def docs(cli):
     """Spin up a local HTTPServer instance for the QMK docs.
     """
     os.chdir('docs')
 
     with http.server.HTTPServer(('', cli.config.docs.port), http.server.SimpleHTTPRequestHandler) as httpd:
-        cli.log.info("Serving QMK docs at http://localhost:%d/", cli.config.docs.port)
+        cli.log.info(f"Serving QMK docs at http://localhost:{cli.config.docs.port}/")
         cli.log.info("Press Control+C to exit.")
 
+        if cli.config.docs.browser:
+            webbrowser.open(f'http://localhost:{cli.config.docs.port}')
+
         try:
             httpd.serve_forever()
         except KeyboardInterrupt: