docs: fix broken cross-reference syntax in get-started tutorial

[chrisbainbridge]

Replace malformed Sphinx ref directives with MyST link syntax.

[Mohit-Chachada]

the proposed change is not incorrect but could you instead just remove the extra backticks to keep things consistent with other such (correct) references:

Suggested change

The slot is the provider of the resource while the plug is the consumer, and a slot can support multiple plug connections. In the above output, the [`camera`](interfaces-camera-interface) interface is not connected because its slot is empty. This means VLC cannot access any connected cameras. The `<snap-name>:<interface-name>` syntax describes which snap is responsible for which component. If there's no snap, such as with `:audio-playback`, the component is directly connected to the system.

The slot is the provider of the resource while the plug is the consumer, and a slot can support multiple plug connections. In the above output, the {ref}`camera <interfaces-camera-interface>` interface is not connected because its slot is empty. This means VLC cannot access any connected cameras. The `<snap-name>:<interface-name>` syntax describes which snap is responsible for which component. If there's no snap, such as with `:audio-playback`, the component is directly connected to the system.

The same applies for other corrections too.

I have opened a PR to fix other such broken refs: #551