asset2base64 - Convert Asset into Base64 String

Converts an uploaded asset (image, zip, audio, video, pdf, ...) or loads and converts the asset from the given URL to a base64 string.
This function can be useful for embedding assets into emails or other applications that require base64-encoded files. Here are some examples of how this function can be used:

• Converting an image file to a base64 string and embedding it into an email.
• Converting a PDF file to a base64 string and sending it to a server for processing.
• Converting an audio file to a base64 string and embedding it into a web page.