Add support to write base64 strings directly to file on platform package

[danielo515]

What is the problem this feature would solve?

I want a way to do something like this using effect platform

await fs.writeFile(filePath, stringData, 'base64');

What is the feature you are proposing to solve the problem?

Probably an extra method called writeStringBase64, or add the encoding option to the existing writeStringFile method

What alternatives have you considered?

Currently I'm wrapping the write file from node using effect, but that is platform specific (but it seems to work both on node and bun)

Discord thread

https://discord.com/channels/795981131316985866/1098177242598756412/1328352928972537956