Add option to wrap embedded file with <details> disclosure element

[kupietools]

Hello @yusanshi, thanks for this useful script. I've added a feature I needed, so I thought you might want to consider it for inclusion in the main.

I added an optional "collapsible" attribute. Adding collapsible=open or collapsible=closed to the parameters you call the script with will wrap the embedded file with <details class="emgithub-details"><summary class="emgithub-summary">[file title]</summary> above the file's contents, then wrap it up with a </details> below, with the default state open or closed, as defined by the chosen value.

[yusanshi]

Thanks for your suggest and sorry for my late reply :)

The idea sounds great but I believe it should be tweaked before being merged into the main branch:

• adding the interface in the frontend, like these
• style, the current style didn't look very well