Feature request: add a search button

[raphmim]

[Daza99]

I was going to make this a separate request but since it would need a search bar i thought to add it to this request.

Implement #hashtags to be part of the search function so we can use tags in our notes and filter them in search. Possibly allow using the + #topicA + #topicD to combine filters.

[KrasnayaPloshchad]

X-plore could do it in both text viewer and editor.