Implemented strict mode for the project (broken tests, hundreds of @ts-ignore and new errors are included) [skip ci]

packages/app/services/loader.ts

@@ -0,0 +1,27 @@
+// On page initialization loader is already visible, so initial value is 1
+let stack = 1;
+
+export function show(): void {
+  if (++stack >= 0) {
+    const loader = document.getElementById('loader');
+
+    if (!loader) {
+      throw new Error('Can not find loader element');
+    }
+
+    loader.classList.add('is-active');
+  }
+}
+
+export function hide(): void {
+  if (--stack <= 0) {
+    stack = 0;
+    const loader = document.getElementById('loader');
+
+    if (!loader) {
+      throw new Error('Can not find loader element');
+    }
+
+    loader.classList.remove('is-active', 'is-first-launch');
+  }
+}