Add Nuke Wars Baikal Map (#2306)

## Description:
This PR adds the Nuke Wars Baikal map (more balanced out than the
original). This is made for the upcoming Nuke Wars gamemode.

## 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

resources/maps/baikalnukewars/manifest.json

@@ -0,0 +1,19 @@
+{
+  "map": {
+    "height": 1564,
+    "num_land_tiles": 1968430,
+    "width": 2500
+  },
+  "map16x": {
+    "height": 391,
+    "num_land_tiles": 120323,
+    "width": 625
+  },
+  "map4x": {
+    "height": 782,
+    "num_land_tiles": 488353,
+    "width": 1250
+  },
+  "name": "Baikal (Nuke Wars)",
+  "nations": []
+}