[plock-1]: add settings file

[jasonjmcghee]

Adds a settings.json file to configure instead of hardcoded vars.

Built to be compatible with a svelte front-end once that's built

Allows for this kind of setup:

{
  "environment": {},
  "ollama": {
    "enabled": true,
    "ollama_model": "openhermes2.5-mistral"
  },
  "custom_commands": {
    "index": 0,
    "custom_commands": [
      {
        "name": "gpt",
        "command": [
          "bash",
          "/Users/jason/workspace/plock/scripts/gpt.sh"
        ]
      }
    ]
  },
  "custom_prompts": {
    "basic_index": 0,
    "with_context_index": 1,
    "custom_prompts": [
      {
        "name": "default basic",
        "prompt": "Say hello, then {}"
      },
      {
        "name": "default with context",
        "prompt": "I will ask you to do something. Below is some extra context to help do what I ask. --------- {} --------- Given the above context, please, {}. DO NOT OUTPUT ANYTHING ELSE."
      }
    ]
  },
  "shortcuts": {
    "basic": "CmdOrControl+Shift+.",
    "with_context": "CmdOrControl+Shift+/"
  }
}

Why are there multiple prompts and commands?
Future-proofing, so we can select them from a list.

Can be dynamically loaded at any time: