Write note to filesystem if file exists

[daniele-athome]

This patch writes note content back to the filesystem if a file exists in the public docs path. This can be a first step towards the real objective of #90 maybe?

Please note that this doesn't address the fact that notes loaded from docsPath are set with a null user owner ID so they are not actually editable. You need to update the row in the database for that. I believe that part should be addressed in another way (I was thinking something like per-user docsPath)

[jackycute]

Hi @daniele-athome, I think this is great! It will be better if there is a config to enable/disable this feature.

[daniele-athome]

I'm sorry but I stopped using CodiMD :cry: