Add updating commands to docs, remove unneccessary resources/folder.

[hoanguyenn2015]

The resources/ folder is generated when running hugoserve, so I think we don't need it in the repo.

I don't know how to update this theme via git submodule and customize it and keep the theme updated without conflicts. Can you give some short guides?

[alex-shpak]

Hi! The resources used to be needed for demo sites before, I will check if it is still needed, tho, it should not affect your site, as far as I know.
Otherwise if you want to customize something in theme, just add it at the same location in your repository, it will override corresponding theme file/template

[alex-shpak]

resources folder has been removed