feat: add external plugin loader and examples for Brainy

Introduced `pluginLoader.ts` to enable loading and configuring augmentation plugins from external packages. Added `examples/externalPlugins.js` to demonstrate usage. Enhanced storage status reporting in `opfsStorage` and `BrainyData` with detailed storage capacity and usage methods. Updated README with an external plugin usage guide.

src/index.ts

@@ -66,6 +66,30 @@ export {
 }
 export type { PipelineOptions }
 
+// Export plugin loader
+import {
+  loadPlugins,
+  configureAndStartPipeline,
+  createSensePluginConfig,
+  createConduitPluginConfig
+} from './pluginLoader.js'
+import type {
+  PluginLoaderOptions,
+  PluginConfig,
+  PluginLoadResult
+} from './pluginLoader.js'
+export {
+  loadPlugins,
+  configureAndStartPipeline,
+  createSensePluginConfig,
+  createConduitPluginConfig
+}
+export type {
+  PluginLoaderOptions,
+  PluginConfig,
+  PluginLoadResult
+}
+
 // Export types
 import type {
   Vector,