Create sv_SE Qwerty layout for ErgoDox

Create sv_SE Qwerty layout for ErgoDox

*NOTE:* it might still be desirable to set the software layout to sv_SE in your
OS.

Swedish (sv_SE) Qwerty layout for ErgoDox, based on the Default configuration

I have tried making this as close of a match I could between the [default
ErgoDox EZ configuration](https://ergodox-ez.com/pages/our-firmware) and a
standard Swedish Qwerty layout.

Notable differences from default:
=================================

* There are three special character buttons (acute accent, circumflex/tilde and
  apostrophe/asterisk) that don't have any buttons to map to naturally. I've put
  these at other places:

    * Acute accent (´) can be found in the lower left corner, conveniently
      placed to reach for making an é.

    * Apostrophe (') was put in the lower left corner, close to acute accent.

    * Circumflex (^) and asterisk (*) was placed in the lower right corner.

    * Tilde (~) and diaeresis (¨) I couldn't find a good place for, so I left
      those out. I could only get the buttons to produce a single one of the
      characters. How can I get it to work properly?

* The Alt button on right thumb was exchanged for AltGr (RAlt).

* I changed the backslash in the numpad (layer 1) for a minus. Thought it was
  more sensible.

* I didn't find a good place for the "<>|" button, so that one was left out.
  That is a problem that really needs to be resolved. Pipe can be found on layer
  one, however.