Add a FAQ about passing arguments to an application

questions/pass-args-to-app.question.md

@@ -0,0 +1,38 @@
+---
+title: "How do I pass arguments to an app?"
+alt_titles:
+  - "pass arguments to an application"
+  - "pass parameters to an app"
+  - "pass parameters to an application"
+---
+
+When creating your `App` class, override `__init__` as you would when
+inheriting normally. For example:
+
+```python
+from textual.app import App, ComposeResult
+from textual.widgets import Static
+
+class Greetings(App[None]):
+
+    def __init__(self, greeting: str="Hello", to_greet: str="World") -> None:
+        self.greeting = greeting
+        self.to_greet = to_greet
+        super().__init__()
+
+    def compose(self) -> ComposeResult:
+        yield Static(f"{self.greeting}, {self.to_greet}")
+```
+
+Then the app can be run, passing in various arguments; for example:
+
+```python
+# Running with default arguments.
+Greetings().run()
+
+# Running with a keyword arguyment.
+Greetings(to_greet="davep").run()
+
+# Running with both positional arguments.
+Greetings("Well hello", "there").run()
+```