docs: convert CLI flags section to table format

Amolith created 

Assisted-by: GLM 4.7 via Crush <crush@charm.land>

Change summary

README.md | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

Detailed changes

README.md 🔗 

@@ -50,9 +50,11 @@ All flags are optional if configured in `~/.config/garble/config.toml`.
 
 ### Flags
 
-- `--provider` — Provider ID (e.g. `openai`, `anthropic`, `google`)
-- `--model` — Model ID (e.g. `gpt-4o`, `claude-3-opus`, `gemini-1.5-pro`)
-- `--directions` — Instructions for how to transform the input
+| Flag           | Description                                 | Example values                              |
+| -------------- | ------------------------------------------- | ------------------------------------------- |
+| `--provider`   | Provider ID                                 | `openai`, `anthropic`, `google`             |
+| `--model`      | Model ID                                    | `gpt-4o`, `claude-3-opus`, `gemini-1.5-pro` |
+| `--directions` | Instructions for how to transform the input | `"fix grammar and spelling"`                |
 
 ### Configuration