:sig
String base64_encode(String raw)

:params
raw : binary-safe source string
return value : Base64 encoded string

:see
>string
base64_decode

:content
Encodes a string with Base64.

UCE strings can contain binary data, so `raw` may include NUL bytes and non-text bytes.

Example:

```uce
String encoded = base64_encode("hello");
// encoded == "aGVsbG8="
```

Related:

- PHP: `base64_encode()`
- JavaScript / Node.js: `Buffer.from(value).toString("base64")`