completion docs

docs/markdown/_toc.md

@@ -22,6 +22,7 @@
 > [General](/cli/general)
 > [Info](/cli/info)
 > [Check](/cli/check)
+> [Completion](/cli/completion)
 > [Backup](/cli/backup)
 > [Restore](/cli/restore)
 > [Forget](/cli/forget)

docs/markdown/cli/completion.md

@@ -0,0 +1,17 @@
+# Completion
+
+```bash
+autorestic completion [bash|zsh|fish|powershell]
+```
+
+Autorestic can generate shell completions automatically to make the experience even easier.
+Supported shells are
+
+- bash
+- zsh
+- fish
+- powershell
+
+To see how to install run `autorestic help completion` and follow the instructions for your specific shell
+
+> :ToCPrevNext