refactor(core): split web entry from core (#6082)

This pr is trying to split `web` and `electron` entries from `core`. It allows more platform-related optimization to be addressed in each entry.
We should remove all browser/electron only codes from `core` eventually, this is the very first step for that.

tools/cli/src/webpack/s3-plugin.ts

@@ -0,0 +1,47 @@
+import { readFile } from 'node:fs/promises';
+import { join } from 'node:path';
+
+import type { PutObjectCommandInput } from '@aws-sdk/client-s3';
+import { PutObjectCommand, S3Client } from '@aws-sdk/client-s3';
+import { lookup } from 'mime-types';
+import type { Compiler, WebpackPluginInstance } from 'webpack';
+
+export const R2_BUCKET =
+  process.env.R2_BUCKET ??
+  (process.env.BUILD_TYPE === 'canary' ? 'assets-dev' : 'assets-prod');
+
+export class WebpackS3Plugin implements WebpackPluginInstance {
+  private readonly s3 = new S3Client({
+    region: 'auto',
+    endpoint: `https://${process.env.R2_ACCOUNT_ID}.r2.cloudflarestorage.com`,
+    credentials: {
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      accessKeyId: process.env.R2_ACCESS_KEY_ID!,
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      secretAccessKey: process.env.R2_SECRET_ACCESS_KEY!,
+    },
+  });
+
+  apply(compiler: Compiler) {
+    compiler.hooks.assetEmitted.tapPromise(
+      'WebpackS3Plugin',
+      async (asset, { outputPath }) => {
+        if (asset === 'index.html') {
+          return;
+        }
+        const assetPath = join(outputPath, asset);
+        const assetSource = await readFile(assetPath);
+        const putObjectCommandOptions: PutObjectCommandInput = {
+          Body: assetSource,
+          Bucket: R2_BUCKET,
+          Key: asset,
+        };
+        const contentType = lookup(asset);
+        if (contentType) {
+          putObjectCommandOptions.ContentType = contentType;
+        }
+        await this.s3.send(new PutObjectCommand(putObjectCommandOptions));
+      }
+    );
+  }
+}