Add type definitions for base64-arraybuffer (#25239)

* Added declarations for 'base64-arraybuffer'

* fix linting and header

types/base64-arraybuffer/base64-arraybuffer-tests.ts

@@ -0,0 +1,4 @@
+import { encode, decode } from 'base64-arraybuffer';
+
+encode(new Float32Array([1, 2, 3]).buffer); // $ExpectType string
+decode('AACAPwAAAEAAAEBA'); // $ExpectType ArrayBuffer

types/base64-arraybuffer/index.d.ts

@@ -0,0 +1,7 @@
+// Type definitions for base64-arraybuffer 0.1
+// Project: https://github.com/niklasvh/base64-arraybuffer
+// Definitions by: Ben Cook <https://github.com/jbencook>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+export function encode(arraybuffer: ArrayBuffer): string;
+export function decode(base64: string): ArrayBuffer;

types/base64-arraybuffer/tsconfig.json

@@ -0,0 +1,23 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "strictFunctionTypes": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "base64-arraybuffer-tests.ts"
+    ]
+}

types/base64-arraybuffer/tslint.json

@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }