docs: add CLI usage and integrate generation in release

www/docs/cli/filebrowser-completion-fish.md

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+# filebrowser completion fish
+
+Generate the autocompletion script for fish
+
+## Synopsis
+
+Generate the autocompletion script for the fish shell.
+
+To load completions in your current shell session:
+
+	filebrowser completion fish | source
+
+To load completions for every new session, execute once:
+
+	filebrowser completion fish > ~/.config/fish/completions/filebrowser.fish
+
+You will need to start a new shell for this setup to take effect.
+
+
+```
+filebrowser completion fish [flags]
+```
+
+## Options
+
+```
+  -h, --help              help for fish
+      --no-descriptions   disable completion descriptions
+```
+
+## Options inherited from parent commands
+
+```
+  -c, --config string     config file path
+  -d, --database string   database path (default "./filebrowser.db")
+```
+
+## See Also
+
+* [filebrowser completion](filebrowser-completion.md)	 - Generate the autocompletion script for the specified shell
+