GitPlugin Does Not Prompt to Add SSH Known Host

### Godot version

4.6.1.stable.official

### Godot Git Plugin version

3.2.1

### System information

Windows 11

### Issue description

When using Git, attempting to connect to a remote via SSH gives a warning that the host is unknown and prompts the user to accept or reject the host. This is desired functionality. However, the plugin simply fails with an error, rather than popping up a window and allowing the user to resolve the issue.

Examples: #293, #299

Sometimes, users have other issues as well, but this simple step obscures whatever their underlying problem is.

I think creating a stop condition that the underlying provider (Git) handles is a core function, which is why I filed this as a bug. It would also reduce issue creation and speed up troubleshooting on real issues.

Feel free to change it to a feature request if you disagree. While I'd like this to be in-built functionality, updating the Wiki to reflect this common scenario wouldn't be the worst solution.

### Steps to reproduce

- Follow the v3 [Wiki](https://github.com/godotengine/godot-git-plugin/wiki/Git-plugin-v3) plugin instructions to install the plugin.

- Attempt to connect to Github (or another remote provider) via SSH _for the first time_ using the Godot plugin

- Encounter the error: `Error -17: invalid or unknown remote ssh hostkey in godot-git-plugin\src\git_plugin.cpp:GitPlugin::_push`