Add postgres database context to chatbot integration

Related to #3 Add logic to fetch and include database schema information in system messages when a `pgPlugin` module is utilized. * **App.tsx** - Add logic to fetch database schema information when a `pgPlugin` module is utilized. - Update the `handleSendMessage` function to include database schema information in the system messages. - Update the `contextMessage` to include the database schema information. * **pgPlugin.tsx** - Update the `PgComponent` to fetch and store database schema information. - Add `schemaInfo` property to `PgModuleType` and `PgComponentProps`. - Add `useEffect` to fetch schema information when database configuration changes. * **main.ts** - Add a function to query the database schema using the provided SQL query. - Update the `ipcMain.handle` to include a handler for fetching the database schema. * **preload.ts** - Expose the method to fetch the database schema to the app. - Update the `contextBridge.exposeInMainWorld` to include the new method. --- For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/williamcotton/guish/issues/3?shareId=bd067e4b-689f-46c2-9067-6d6a8d98533d).