add gallery element

...eguide/templates/patterns/atoms/buttons/round_button.html

...eguide/templates/patterns/atoms/buttons/round_button.yaml

...templates/patterns/atoms/buttons/round_button_colors.html

majak_uistyleguide/templates/patterns/atoms/table/table.html

..._uistyleguide/templates/patterns/atoms/text/headings.html

...leguide/templates/patterns/molecules/gallery/gallery.html

...leguide/templates/patterns/molecules/gallery/gallery.yaml

package.json

src/js/main.js