docs(base64): Add readme and news
MODIFY
packages/base64/NEWS.md
packages/base64/NEWS.md
+User-visible changes in base64:
+
+## Next version: v0.1.0
+
+- Initial version.

MODIFY
packages/base64/README.md
packages/base64/README.md
+# base64
+
+Base64 is a JavaScript package that encodes and decodes
+[Base64](https://en.wikipedia.org/wiki/Base64) between strings and
+`Uint8Array`s.
+
+Base64 exports TypeScript definitions and is suitable for both web and Node.js.
+
+## Install
+
+```sh
+npm install @endo/base64
+```
+
+## Usage
+
+```js
+import { encodeBase64, decodeBase64 } from '../src/main.js';
+
+const string = encodeBase64(bytes);
+const bytes = decodeBase64(string);
+```

docs(base64): Add readme and news