chore: import node types (#44172)

* chore: add @types/node to client

* fix: update declaration with node 16 changes

client/package.json

@@ -136,6 +136,7 @@
     "@types/jest": "26.0.24",
     "@types/loadable__component": "5.13.4",
     "@types/lodash-es": "4.17.5",
+    "@types/node": "^16.11.7",
     "@types/prismjs": "1.16.6",
     "@types/psl": "1.1.0",
     "@types/reach__router": "1.3.9",

client/src/declarations.d.ts

@@ -15,19 +15,17 @@ declare module '*.png' {
   export default content;
 }
 
-declare namespace NodeJS {
-  interface Global {
-    MathJax: {
-      Hub: {
-        Config: (attributes: {
-          tex2jax: {
-            inlineMath: Array<string[]>;
-            processEscapes: boolean;
-            processClass: string;
-          };
-        }) => void;
-        Queue: (attributes: unknown[]) => void;
+// This has to be declared as var, not let or const, to be added to globalThis
+// eslint-disable-next-line no-var
+declare var MathJax: {
+  Hub: {
+    Config: (attributes: {
+      tex2jax: {
+        inlineMath: Array<string[]>;
+        processEscapes: boolean;
+        processClass: string;
       };
-    };
-  }
-}
+    }) => void;
+    Queue: (attributes: unknown[]) => void;
+  };
+};