Add a new national RSE Chapter

Contributing RSE chapters are defined in the _data/committee/national_chapters.yml file. They basically have the same structure as a contributing member, but with small differences. Suppose, you want to add the uk-RSE chapter, then keep in mind that

1. you add it as a dictionary item, i.e.

   deRSE:
       name: ...

   instead of

   - name: ...

   (the latter would be what you do to add a committee member)
2. the key must not contain dashes (-)
3. you must not add teams to the config
4. you need to specify an internal link, in our case

       internal: /contact/#ukRSE

5. you should rather use the long_name attribute instead of the affiliation (see the card elements).