Adding file append

[ikhsan]

Thanks for Files! I wrote a script with it for a database validation task at work, had a very nice warm feeling being able to write Swift scripts 😄

I have a suggestion though, I was a bit surprised that Files's writes only override but no support for appending. Can we have file append? Similar to >> in bash.

I'm happy to create a PR, but I want to make sure if this sounds like a good addition. I'm thinking to add new methods func append(data: Data) throws and its string counterpart. Or, we could change write to func write(data: Data, shouldAppend: Bool = false) throws. I prefer the former though, let me know what you think.

[JohnSundell]

Hi @ikhsan! 👋 Awesome to hear that you're getting into Swift scripting 👍 I agree, let's do the former:

func append(data: Data) throws

Think it would be a great addition to the framework, happy to accept a PR adding it 🙂

[ikhsan]

Awesome stuff! 👌

As the PR is ready #49, I'm closing this issue.