Add /next command

[rtix]

/next, /qn command to load next file in playlist. I find it useful for me, hence the proposal

[Et0h]

Nice work. I've tested it and it operates correctly. It's a simple change to do the code so shouldn't add any bugs, and I can see why it would be useful for those controlling Syncplay through command line and mpv.

Unless anyone objects I'd say it's good to accept, with the remaining tasks being to:

• Add stubs for the "commandList-notification/next" message in other languages
• Add entry for the /next command to https://github.com/Syncplay/syncplay/blob/master/docs/syncplay.1
• Add entry to the manual on the website based on the explanations already provided.

[rtix]

@Et0h I've added stubs, but I'm not sure how this command should look like in docs and how do I contribute to website?

[Et0h]

@Et0h I've added stubs, but I'm not sure how this command should look like in docs and how do I contribute to website?

Only I can update the website. I'll do the docs as well.

[Et0h]

Just checked and at present manual is only for command line options, not /commands. As such I've just updated the website.