Add generic PluginNodes to the RootNode

[lorisleiva]

There is still a lot to explore here so this issue mainly offer a space to discuss this in more detail before committing to this.

The main idea here is to allow ecosystem users to extend the Codama IDL using customisable PluginNodes that can be understood by anyone that wishes to support that plugin.

For instance, here's a rough implementation proposal for illustration purposes:

type PluginNode<
  TName extends CamelCaseString = CamelCaseString,
  TData extends object = object
> = {
  kind: 'pluginNode';
  name: TName;
  data: TData;
}

Such that:

type RootNode = {
  kind: 'rootNode';
  program: ProgramNode;
  plugins: PluginNode[];
  // ...
}

Now, imagine the following two concrete plugins:

type Language = "en" | "fr" | "es"
type TranslationPluginNode = PluginNode<
  'translation',
  Record<Language, Record<CamelCaseString, { name: string, docs?: string[] }>>
>

type InstructionSummaryPluginNode = PluginNode<
  'instructionSummary',
  Record<CamelCaseString, string>
>

Which could be used in that way:

const plugins: PluginNode[] = [
  {
    kind: 'pluginNode',
    name: 'translation',
    data: {
      'fr': {
        'transferSol': { name: 'transfertDeSol', docs: [...] },
        'nonceState': { name: 'étatDuNonce' },
      },
      'es': {
        'transferSol': { name: 'transferenciaDeSol', docs: [...] },
        'nonceState': { name: 'estadoDelNonce' },
      },
    },
  },
  {
    kind: 'pluginNode',
    name: 'instructionSummary',
    data: {
      'transferSol': 'Transfer $amount SOL from $source to $destination',
      'createAccount': 'Create a new account $account with $space bytes on the $programId program',
    },
  },
];