install: add depdendency on typing_extensions

docs/installation.md

@@ -23,6 +23,7 @@ The `udev` package must be installed and its daemon running.
 Solaar requires Python 3.7+ and requires several packages to be installed.
 If you are running the system version of Python you should have the
 `python3-pyudev`, `python3-psutil`, `python3-xlib`, `python3-evdev`,
+`python3-typing-extensions`,
 and `python3-yaml` or `python3-pyyaml` packages installed.
 
 To run the GUI Solaar also requires Gtk3 and its GObject introspection bindings.

setup.py

@@ -66,6 +66,7 @@ For instructions on installing Solaar see https://pwr-solaar.github.io/Solaar/in
         'PyYAML (>= 3.12)',
         'python-xlib (>= 0.27)',
         'psutil (>= 5.4.3)',
+        'typing_extensions (>=4.0.0)',
     ],
     extras_require={
         'report-descriptor': ['hid-parser'],