Add font support for base64 format

[YatogamiMikoto]

Hi Developers,
We are using your library to build reports for our application

Motivation

The problem arose when we wanted to add custom fonts to our report. Even though the library supports custom fonts, if the font file is present in a file directory.

We don't have a server to store a .ttf file to use the custom font.

Proposed Solution

We would be storing the .ttf file in a cloud server and fetching the file as base64 and this base64 as the source of .ttf file in the html code whose PDF is to be converted.

Can you please add a feature to your code base such that this .ttf file can be decoded and be used as a source for custom font.