docs: describe asdf_updates_disabled file purpose (#1013)

docs/manage/configuration.md

@@ -60,3 +60,9 @@ legacy_version_file = yes
 - `ASDF_DEFAULT_TOOL_VERSIONS_FILENAME` - The filename of the file storing the tool names and versions. Defaults to `.tool-versions`. Can be any valid filename. Typically you should not override the default value unless you know you want asdf to ignore `.tool-versions` files.
 - `ASDF_DIR` - Defaults to `~/.asdf` - Location of the `asdf` scripts. If you install `asdf` to some other directory, set this to that directory. For example, if you are installing via the AUR, you should set this to `/opt/asdf-vm`.
 - `ASDF_DATA_DIR` - Defaults to `~/.asdf` - Location where `asdf` install plugins, shims and installs. Can be set to any location before sourcing `asdf.sh` or `asdf.fish` mentioned in the section above.
+
+## Internal Configuration
+
+Users should not worry about this section as it describes configuration internal to `asdf` useful for Package Managers and integrators.
+
+- `$ASDF_DIR/asdf_updates_disabled`: Updates via the `asdf update` command are disabled when this file is present (content irrelevant). This is used by Package Managers like Pacman or Homebrew to ensure the correct update method is used for the particular installation.