feat: migrate SlowBuffer to Buffer.allocUnsafeSlow()

Add codemod to handle deprecated SlowBuffer API migration
covering CommonJS, ES6 imports, and usage patterns

Closes: #125 (comment)

Author: lluisemper

package-lock.json

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+# SlowBuffer to Buffer.allocUnsafeSlow Codemod
+
+This codemod migrates deprecated `SlowBuffer` usage to `Buffer.allocUnsafeSlow()` to handle Node.js DEP0030.
+
+## What it does
+
+This codemod transforms:
+
+1. `SlowBuffer` constructor calls to `Buffer.allocUnsafeSlow()`
+2. Direct `SlowBuffer` calls to `Buffer.allocUnsafeSlow()`
+3. Import/require statements to use `Buffer` instead of `SlowBuffer`
+
+## Examples
+
+### Before
+
+```javascript
+const SlowBuffer = require("buffer").SlowBuffer;
+
+// Using SlowBuffer constructor
+const buf1 = new SlowBuffer(1024);
+const buf2 = SlowBuffer(512);
+
+// Direct import
+const { SlowBuffer } = require("buffer");
+const buf3 = new SlowBuffer(256);
+```
+
+### After
+
+```javascript
+const Buffer = require("buffer").Buffer;
+
+// Using Buffer.allocUnsafeSlow()
+const buf1 = Buffer.allocUnsafeSlow(1024);
+const buf2 = Buffer.allocUnsafeSlow(512);
+
+// Direct import
+const { Buffer } = require("buffer");
+const buf3 = Buffer.allocUnsafeSlow(256);
+```
+
+### ESM Support
+
+```javascript
+// Before
+import { SlowBuffer } from "buffer";
+const buf = new SlowBuffer(1024);
+
+// After
+import { Buffer } from "buffer";
+const buf = Buffer.allocUnsafeSlow(1024);
+```

recipes/slow-buffer-to-buffer-alloc-unsafe-slow/README.md

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+schema_version: "1.0"
+name: "@nodejs/slow-buffer-to-buffer-alloc-unsafe-slow"
+version: "1.0.0"
+description: Handle DEP0030 via transforming SlowBuffer usage to Buffer.allocUnsafeSlow().
+author: lluisemper(Lluis Semper Lloret)
+license: MIT
+workflow: workflow.yaml
+category: migration
+
+targets:
+  languages:
+    - javascript
+    - typescript
+
+keywords:
+  - transformation
+  - migration
+  - buffer
+  - slowbuffer
+
+registry:
+  access: public
+  visibility: public

recipes/slow-buffer-to-buffer-alloc-unsafe-slow/codemod.yaml

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+{
+  "name": "@nodejs/slow-buffer-to-buffer-alloc-unsafe-slow",
+  "version": "1.0.0",
+  "description": "Handle DEP0030 via transforming SlowBuffer usage to Buffer.allocUnsafeSlow().",
+  "type": "module",
+  "scripts": {
+    "test": "npx codemod jssg test -l typescript ./src/workflow.ts ./"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/nodejs/userland-migrations.git",
+    "directory": "recipes/slow-buffer-to-buffer-alloc-unsafe-slow",
+    "bugs": "https://github.com/nodejs/userland-migrations/issues"
+  },
+  "author": "lluisemper(Lluis Semper Lloret)",
+  "license": "MIT",
+  "homepage": "https://github.com/nodejs/userland-migrations/blob/main/recipes/slow-buffer-to-buffer-alloc-unsafe-slow/README.md",
+  "dependencies": {
+    "@nodejs/codemod-utils": "*"
+  },
+  "devDependencies": {
+    "@codemod.com/jssg-types": "^1.0.3"
+  }
+}