New Map! "Four Islands" 🏝️ (#2482)

## Description:

Made a type of map we don't already have: Small square map, one Island
in each corner. Could be great for boat gameplay or maybe even nuke
wars.

The special thing is: **All islands are exactly 25% of the territory!**
Was a lot of work drawing that in GIMP...

<img width="1164" height="1168" alt="Screenshot 2025-11-20 000839"
src="https://github.com/user-attachments/assets/ad8345c7-562d-49e8-b367-12be9274f3e4"
/>

<img width="1227" height="1222" alt="Screenshot 2025-11-20 000633"
src="https://github.com/user-attachments/assets/f7e2c58a-fcb3-4e07-91f2-aead5f497fad"
/>

<img width="361" height="288" alt="Screenshot 2025-11-20 000655"
src="https://github.com/user-attachments/assets/120f82ef-2d19-497b-8a31-819e30013c89"
/>

<img width="756" height="282" alt="Screenshot 2025-11-20 005949"
src="https://github.com/user-attachments/assets/8ee04da3-d5fa-4ec9-9e99-9e30ebda2b78"
/>

## 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:

FloPinguin

---------

Co-authored-by: Evan <evanpelle@gmail.com>

resources/lang/en.json

@@ -210,7 +210,8 @@
     "pluto": "Pluto",
     "montreal": "Montreal",
     "achiran": "Achiran",
-    "baikalnukewars": "Baikal (Nuke Wars)"
+    "baikalnukewars": "Baikal (Nuke Wars)",
+    "fourislands": "Four Islands"
   },
   "map_categories": {
     "continental": "Continental",

resources/maps/fourislands/manifest.json

@@ -0,0 +1,44 @@
+{
+  "map": {
+    "height": 1500,
+    "num_land_tiles": 517044,
+    "width": 1500
+  },
+  "map16x": {
+    "height": 375,
+    "num_land_tiles": 31134,
+    "width": 375
+  },
+  "map4x": {
+    "height": 750,
+    "num_land_tiles": 127644,
+    "width": 750
+  },
+  "name": "Four Islands",
+  "nations": [
+    {
+      "coordinates": [403, 1296],
+      "flag": "",
+      "name": "Korinthal",
+      "strength": 2
+    },
+    {
+      "coordinates": [1152, 1251],
+      "flag": "",
+      "name": "Lunareth",
+      "strength": 2
+    },
+    {
+      "coordinates": [1328, 322],
+      "flag": "",
+      "name": "Sylvoria",
+      "strength": 2
+    },
+    {
+      "coordinates": [114, 121],
+      "flag": "",
+      "name": "Myrkwind",
+      "strength": 2
+    }
+  ]
+}