make datepicker popup optional

First I'd like to congratulate you on this piece of software! It looks really refreshingly simple yet powerful. I've been searching for a simple document management system for home use for a long time.

Anyway. I have a few **smaller nitpicks** that could be converted into seperate issues at your discretion:

* The "Notes" editor is a little weird. It's nice that it supports Markdown but once created, the note doesn't feel well-integrated yet. Why is it highlighted with a greenish colour? And why isn't it used -- at least in an abbreviated form -- for the item card in the "gallery view" when searching for documents?

* In the main view I would like to be able to browse by category or tag. I don't want a full "folder"-like implementation. Actually this is probably one of the reasons why it feels so nice and simple, because it doesn't attempt to mimick a file explorer window .. but sometimes I would like to be able to *browse* by category without a specific search term in mind. (I am aware I can search for a tag without any other search terms and that works but its not quite the same thing.)

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**Now what this issue is actually about ...** the datepicker in the metadata editor is really going on my nerves. :grimacing:

* I would really prefer if it were *optional* and hidden behind a button in the input field or at least would not pop up immediately when there is a manually entered date in the field already.

* Or at least don't cover the input field when it does pop up. :yum:


* I am used to enter dates in ISO format like `2020-07-21`. The parser for this field apparently understands this, so that's nice. That would have been more obvious though if I could enter dates manually more comfortably. :smiley:
(I haven't seen any suggestions yet, possibly because the dates in my documents are formatted in German like `21.07.2020`?)