Difficulty translation key (#1959)

Move the key to name mapping for difficulties into the translation
system.

- [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

resources/lang/en.json

@@ -250,9 +250,9 @@
   },
   "difficulty": {
     "difficulty": "Difficulty",
-    "Relaxed": "Relaxed",
-    "Balanced": "Balanced",
-    "Intense": "Intense",
+    "Easy": "Relaxed",
+    "Medium": "Balanced",
+    "Hard": "Intense",
     "Impossible": "Impossible"
   },
   "game_mode": {

src/client/HostLobbyModal.ts

@@ -23,7 +23,6 @@ import {
 import { generateID } from "../core/Util";
 import "./components/baseComponents/Modal";
 import "./components/Difficulties";
-import { DifficultyDescription } from "./components/Difficulties";
 import "./components/Maps";
 import { JoinLobbyEvent } from "./Main";
 import { renderUnitTypeOptions } from "./utilities/RenderUnitTypeOptions";
@@ -240,9 +239,7 @@ export class HostLobbyModal extends LitElement {
                         .difficultyKey=${key}
                       ></difficulty-display>
                       <p class="option-card-title">
-                        ${translateText(
-                          `difficulty.${DifficultyDescription[key as keyof typeof DifficultyDescription]}`,
-                        )}
+                        ${translateText(`difficulty.${key}`)}
                       </p>
                     </div>
                   `,

src/client/SinglePlayerModal.ts

@@ -16,11 +16,6 @@ import {
 import { UserSettings } from "../core/game/UserSettings";
 import { TeamCountConfig } from "../core/Schemas";
 import { generateID } from "../core/Util";
-import "./components/baseComponents/Button";
-import "./components/baseComponents/Modal";
-import "./components/Difficulties";
-import { DifficultyDescription } from "./components/Difficulties";
-import "./components/Maps";
 import { getCosmetics } from "./Cosmetics";
 import { FlagInput } from "./FlagInput";
 import { JoinLobbyEvent } from "./Main";
@@ -150,9 +145,7 @@ export class SinglePlayerModal extends LitElement {
                         .difficultyKey=${key}
                       ></difficulty-display>
                       <p class="option-card-title">
-                        ${translateText(
-                          `difficulty.${DifficultyDescription[key as keyof typeof DifficultyDescription]}`,
-                        )}
+                        ${translateText(`difficulty.${key}`)}
                       </p>
                     </div>
                   `,

src/client/components/Difficulties.ts

@@ -1,13 +1,6 @@
 import { LitElement, css, html } from "lit";
 import { customElement, property } from "lit/decorators.js";
 
-export enum DifficultyDescription {
-  Easy = "Relaxed",
-  Medium = "Balanced",
-  Hard = "Intense",
-  Impossible = "Impossible",
-}
-
 @customElement("difficulty-display")
 export class DifficultyDisplay extends LitElement {
   @property({ type: String }) difficultyKey = "";