Доработки по markdown отображению

> Related #162 

- [ ] `<details/>` html
![image](https://user-images.githubusercontent.com/42924400/100803700-a7090380-343c-11eb-8aaa-18b0dd9b95bb.png)

- [ ] local `<img />` html
![image](https://user-images.githubusercontent.com/42924400/100803757-c142e180-343c-11eb-8554-b893fedcd18d.png)
