These custom components can be used in contentful content part. These are just simple html declarations, and in our side we will create a custom components from them. They are mainly used for pre-formatting the text / data or add extra feature to the site.
It will create a submenu item for custom pages. By clicking on these menu item, they will scroll to that part of the page.
<submenu-item>2020</<submenu-item>
It will create a custom text which based on stern font, the text will be transformed to uppercase variant.
code:
<stern>Your text here</stern>