Add verbose output to the documentation help section (#15915)

Closes #15914

Author: zanieb

docs/getting-started/help.md

@@ -30,6 +30,23 @@ $ uv help init
 When using the long help menu, uv will attempt to use `less` or `more` to "page" the output so it is
 not all displayed at once. To exit the pager, press `q`.
 
+## Displaying verbose output
+
+The `-v` flag can be used to display verbose output for a command, e.g., for `uv sync`:
+
+```console
+$ uv sync -v
+```
+
+The `-v` flag can be repeated to increase verbosity, e.g.:
+
+```console
+$ uv sync -vv
+```
+
+Often, the verbose output will include additional information about why uv is behaving in a certain
+way.
+
 ## Viewing the version
 
 When seeking help, it's important to determine the version of uv that you're using — sometimes the