Adopt lerna and typescript

packages/core-mt/package.json

@@ -0,0 +1,50 @@
+{
+  "name": "@ffmpeg/core-mt",
+  "version": "0.11.0",
+  "description": "ffmpeg.wasm core",
+  "main": "./dist/ffmpeg-core.cjs",
+  "types": "./types/ffmpeg-core.d.ts",
+  "exports": {
+    ".": {
+      "types": "./types/ffmpeg-core.d.ts",
+      "import": "./dist/ffmpeg-core.js",
+      "require": "./dist/ffmpeg-core.cjs"
+    }
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/ffmpegwasm/ffmpeg.wasm.git"
+  },
+  "keywords": [
+    "ffmpeg",
+    "webassembly",
+    "video",
+    "audio",
+    "transcode"
+  ],
+  "author": "jeromewus@gmail.com",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/ffmpegwasm/ffmpeg.wasm/issues"
+  },
+  "homepage": "https://github.com/ffmpegwasm/ffmpeg.wasm#readme",
+  "publishConfig": {
+    "access": "public"
+  },
+  "files": [
+    "dist",
+    "types"
+  ],
+  "scripts": {
+    "lint": "eslint types"
+  },
+  "dependencies": {
+    "@types/emscripten": "^1.39.6"
+  },
+  "devDependencies": {
+    "@typescript-eslint/eslint-plugin": "^5.37.0",
+    "@typescript-eslint/parser": "^5.37.0",
+    "eslint": "^8.23.1",
+    "typescript": "^4.8.3"
+  }
+}

packages/core-mt/tsconfig.json

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+{
+  "extends": "../../tsconfig.json"
+}

packages/core-mt/types/ffmpeg-core.d.ts

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+/// <reference types="emscripten" />
+
+type Pointer = number;
+type StringArrayPointer = Pointer;
+
+interface FFmpegCoreModule extends EmscriptenModule {
+  _ffmpeg: (number, StringArrayPointer) => number;
+}
+declare const createFFmpegCore: EmscriptenModuleFactory<FFmpegCoreModule>;
+export default createFFmpegCore;