Toggle stricter compilation rules in tsconfig

Now the whole codebase needs to be fixed. Every file.

tsconfig.json

@@ -2,9 +2,30 @@
   "compilerOptions": {
     "target": "ES2020",
     "module": "ESNext",
-    "lib": ["ES2020", "DOM", "DOM.Iterable"],
+    "lib": [
+      "ES2020",
+      "DOM",
+      "DOM.Iterable"
+    ],
     "skipLibCheck": true,
-
+    // Strict mode (9)
+    "strict": true,
+    "alwaysStrict": true,
+    "noImplicitAny": true,
+    "noImplicitThis": true,
+    "strictNullChecks": true,
+    "strictBindCallApply": true,
+    "strictFunctionTypes": true,
+    "strictPropertyInitialization": true,
+    "useUnknownInCatchVariables": true,
+    // No unused code (4)
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "allowUnusedLabels": false,
+    "allowUnreachableCode": false,
+    // No implicit code (2)
+    "noImplicitOverride": true,
+    "noImplicitReturns": true,
     /* Bundler mode */
     "moduleResolution": "bundler",
     "esModuleInterop": true,
@@ -12,14 +33,15 @@
     "resolveJsonModule": true,
     "isolatedModules": true,
     "noEmit": true,
-
-    /* Linting */
-    "strict": true,
-    "forceConsistentCasingInFileNames": true,
-    "useDefineForClassFields": true,
-    "noUnusedLocals": true,
-    "noUnusedParameters": true,
-    "noFallthroughCasesInSwitch": true
+    // Others (5)
+    "noUncheckedIndexedAccess": true,
+    "noPropertyAccessFromIndexSignature": true,
+    "noFallthroughCasesInSwitch": true,
+    "exactOptionalPropertyTypes": true,
+    "forceConsistentCasingInFileNames": true
   },
-  "include": ["src", "../definitions/"]
+  "include": [
+    "src",
+    "../definitions/"
+  ]
 }