feat: Test running overhaul, switch to Prettier & reformat everything (#1407)

* chore: Switch to Node 20 + Vitest

* chore: migrate to vitest mock functions

* chore: code style (switch to prettier)

* test: re-enable long-running test

Seems the switch to Node 20 and Vitest has vastly improved the code's and / or the test's runtime!

see #1193

* chore: code style

* chore: fix failing tests

* Updated Documentation in README.md

* Update contribution guidelines to state usage of Prettier

* fix: set prettier printWidth back to 80

* chore: apply updated code style automatically

* fix: set prettier line endings to lf again

* chore: apply updated code style automatically

---------

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>

Maths/PrimeCheck.js

@@ -1,25 +1,25 @@
-/*
-  Modified from:
-    https://github.com/TheAlgorithms/Python/blob/master/maths/prime_check.py
-
-  Complexity:
-    O(sqrt(n))
-*/
-
-const PrimeCheck = (n) => {
-  // input: n: int
-  // output: boolean
-  if (n === 1) return false
-  if (n === 0) return false
-  if (n === 2) return true
-  if (n % 2 === 0) return false
-
-  for (let i = 3; i * i <= n; i += 2) {
-    if (n % i === 0) {
-      return false
-    }
-  }
-  return true
-}
-
-export { PrimeCheck }
+/*
+  Modified from:
+    https://github.com/TheAlgorithms/Python/blob/master/maths/prime_check.py
+
+  Complexity:
+    O(sqrt(n))
+*/
+
+const PrimeCheck = (n) => {
+  // input: n: int
+  // output: boolean
+  if (n === 1) return false
+  if (n === 0) return false
+  if (n === 2) return true
+  if (n % 2 === 0) return false
+
+  for (let i = 3; i * i <= n; i += 2) {
+    if (n % i === 0) {
+      return false
+    }
+  }
+  return true
+}
+
+export { PrimeCheck }