chore: import upstream snapshot with attribution

apps/webapp/app/lib.es5.d.ts

@@ -0,0 +1,19 @@
+type Falsy = false | 0 | "" | null | undefined;
+
+interface Array<T> {
+  /**
+   * Returns the elements of an array that meet the condition specified in a callback function.
+   * @param predicate A function that accepts up to three arguments. The filter method calls the predicate function one time for each element in the array.
+   * @param thisArg An object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.
+   */
+  filter<S extends T>(predicate: BooleanConstructor, thisArg?: any): Exclude<S, Falsy>[];
+}
+
+// See this for more: https://twitter.com/mattpocockuk/status/1653403198885904387?s=20
+export type Prettify<T> = {
+  [K in keyof T]: T[K];
+} & {};
+
+export type EnsureProperty<T, K extends keyof T> = T & {
+  [P in K]-?: NonNullable<T[P]>;
+};