docs(README.md): add alternative ways to run OpenCommit via npx and bunx

The README.md file has been updated to include alternative ways to run OpenCommit via the `npx opencommit` and `bunx opencommit` commands. This provides users with more options to execute the tool without the need for a global installation.

Author: di-sukharev

README.md

@@ -28,6 +28,8 @@ You can use OpenCommit by simply running it via the CLI like this `oco`. 2 secon
    npm install -g opencommit
    ```
 
+   Alternatively run it via `npx opencommit` or `bunx opencommit`
+
    MacOS may ask to run the command with `sudo` when installing a package globally.
 
 2. Get your API key from [OpenAI](https://platform.openai.com/account/api-keys). Make sure that you add your payment details, so the API works.