Fix dead players sending alliance requests (#1508)

## Description:

Prevent unholly alliances with the undead.

## 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
- [x] I have read and accepted the CLA aggreement (only required once).

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

IngloriousTom

tests/PlayerImpl.test.ts

@@ -98,4 +98,13 @@ describe("PlayerImpl", () => {
 
     expect(ports.length).toBe(3);
   });
+
+  test("Can't send alliance requests when dead", () => {
+    // conquer other
+    const otherTiles = other.tiles();
+    for (const tile of otherTiles) {
+      player.conquer(tile);
+    }
+    expect(other.canSendAllianceRequest(player)).toBe(false);
+  });
 });