Add Svalmel (#2600)

## Description:
This PR adds the Christmas map Svalmel with 5 nations.

Describe the PR.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

DISCORD_USERNAME
Nikola123

src/client/components/Maps.ts

@@ -39,6 +39,7 @@ export const MapDescription: Record<keyof typeof GameMapType, string> = {
   Achiran: "Achiran",
   BaikalNukeWars: "Baikal (Nuke Wars)",
   FourIslands: "Four Islands",
+  Svalmel: "Svalmel",
   GulfOfStLawrence: "Gulf of St. Lawrence",
   Lisbon: "Lisbon",
 };