I'll second TiddlyWiki. I've used it for several years and became a fan early on.
These days you might run across some hiccups in getting it to work in your browser of choice. Over the years the browser vendors became less and less inclined to allow javascript and extensions attain local file editing permissions. That's pretty reasonable, but annoying.
A pretty decent alternative that I've been using for months, now, is an app called Tiddly Desktop. It's an NW.js-based app so it has no trouble accessing the local filesystems.
It's a single, self-contained HTML file. You download it, add data, then overwrite the file with a new version which includes changes.
If you want to go fancy, you can install it on a server with Node.js and stuff, but there's not a need to go there.
[1]https://tiddlywiki.com/