Streamable output refresh is size limited to 4k, won't allow | image=(base64data)

[peanball]

Describe the bug
The streamable plugin option reads data from the script's output stream and forwards it to the streamable output processing, which checks for ~~~. The reading is buffered and by system defaults limited to ca. 4k, while the rest of the stream may not be read.

To Reproduce
Produce an image output:

echo "~~~
some image | image=$(base64 -b 0 -o - -i img.png)
"

This should produce a complete image but the image is broken.

Expected behavior
The image is loaded properly

Screenshots

Environment:

• macOS version: 13.0
• SwiftBar version: 1.4.4

Plugin Example:
Sample plugin to reproduce the issue, link or code.

(not tested. I will test later and in more detail)

echo "~~~
some image | image=$(base64 -b 0 -o - -i img.png)
"

Additional Context:

• I don't run Bartender/Dozer/etc. or tested the issue without it running

I am currently working on a streaming version of the iTunes / Music status "Now Playing" plugin and wanted to add album art. The script works fine but the album art doesn't load.

If I find time before you, I might open a PR with a fix. I can test changes and have the above now playing script that is an extensive "test suite".

I found the edge case that wasn't handled in the stream output processing and propose a simple fix in #372.