Adds Milky Way Map (#3519)

## Description:

Adds Milky Way galaxy map based on real reconstruction by NASA. Star
density simulated as terrain. Best played in Dark Mode.

Also adds credits to JPL NASA

<img width="532" height="533" alt="Captura de pantalla 2026-03-26
142938"
src="https://github.com/user-attachments/assets/87bb19bb-4e2d-4383-a3e9-6e14b714b84c"
/>

## 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:

tri.star1011

resources/maps/milkyway/manifest.json

@@ -0,0 +1,50 @@
+{
+  "map": {
+    "height": 1500,
+    "num_land_tiles": 442979,
+    "width": 1500
+  },
+  "map16x": {
+    "height": 375,
+    "num_land_tiles": 24807,
+    "width": 375
+  },
+  "map4x": {
+    "height": 750,
+    "num_land_tiles": 106678,
+    "width": 750
+  },
+  "name": "milkyway",
+  "nations": [
+    {
+      "coordinates": [775, 757],
+      "flag": "",
+      "name": "Sagittarius A*"
+    },
+    {
+      "coordinates": [967, 247],
+      "flag": "",
+      "name": "Perseus Arm"
+    },
+    {
+      "coordinates": [478, 1139],
+      "flag": "",
+      "name": "Centaurus Arm"
+    },
+    {
+      "coordinates": [840, 1048],
+      "flag": "un",
+      "name": "Empire of Mankind"
+    },
+    {
+      "coordinates": [1055, 1330],
+      "flag": "",
+      "name": "Aliens"
+    },
+    {
+      "coordinates": [531, 164],
+      "flag": "Cthulhu Republic",
+      "name": "The Void"
+    }
+  ]
+}