Feat: Alphanumeric Coordinate Grid on Alternate View (#2938)

## Description:

Adds a coordinate grid to the Alternate View (holding spacebar) using
numbers on the X-axis, and letters on the Y-axis. No more "he's
attacking you in that—well, the little peninsula thing... next to the
island! which island? uhh..." moments when playing with friends.
Optimally maps have letters A-J (just like in the Battleships board
game) but special maps like Amazon River dynamically resize to only have
2 letters so as to not have too many number columns. This feature
overall can be toggled via the settings menu.

Also saw it requested on the [official
discord](https://discord.com/channels/1359946986937258015/1457037351422263480)
a couple times, thought it was a neat idea.

### World Map
<img width="3809" height="1824" alt="image"
src="https://github.com/user-attachments/assets/dab56879-a34e-48ea-a588-2907d26feb45"
/>

### Scales correctly when zoomed in
<img width="3798" height="1874" alt="image"
src="https://github.com/user-attachments/assets/7e06a47f-d3d9-4f92-8e89-3eaf866e9b25"
/>

### Amazon River
<img width="3803" height="1595" alt="image"
src="https://github.com/user-attachments/assets/4797c576-20b2-4aa8-8b7a-107078ab6308"
/>

### Enable/Disable via settings


https://github.com/user-attachments/assets/ec9f4e07-70a1-4f9d-b137-c3c3d2a2540c

## 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:

bijx

---------

Co-authored-by: iamlewis <lewismmmm@gmail.com>

src/client/UserSettingModal.ts

@@ -22,6 +22,7 @@ const isMac =
 
 const DefaultKeybinds: Record<string, string> = {
   toggleView: "Space",
+  coordinateGrid: "KeyM",
   buildCity: "Digit1",
   buildFactory: "Digit2",
   buildPort: "Digit3",
@@ -491,6 +492,16 @@ export class UserSettingModal extends BaseModal {
         @change=${this.handleKeybindChange}
       ></setting-keybind>
 
+      <setting-keybind
+        action="coordinateGrid"
+        label=${translateText("user_setting.coordinate_grid_label")}
+        description=${translateText("user_setting.coordinate_grid_desc")}
+        defaultKey=${DefaultKeybinds.coordinateGrid}
+        .value=${this.getKeyValue("coordinateGrid")}
+        .display=${this.getKeyChar("coordinateGrid")}
+        @change=${this.handleKeybindChange}
+      ></setting-keybind>
+
       <h2
         class="text-blue-200 text-xl font-bold mt-8 mb-3 border-b border-white/10 pb-2"
       >