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>

Bit-Manipulation/BinaryCountSetBits.js

@@ -7,7 +7,7 @@
 
 */
 
-function BinaryCountSetBits (a) {
+function BinaryCountSetBits(a) {
   'use strict'
 
   // check whether input is an integer, some non-integer number like, 21.1 have non-terminating binary expansions and hence their binary expansion will contain infinite ones, thus the handling of non-integers (including strings,objects etc. as it is meaningless) has been omitted

Bit-Manipulation/IsPowerofFour.js

@@ -12,6 +12,6 @@
  * const result = isPowerOfFour(16); // Returns true (16 is 4^2)
  * const result2 = isPowerOfFour(5);  // Returns false (5 is not a power of four)
  */
-const isPowerOfFour = (n) => ((n > 0) && ((n & n - 1) === 0) && (n % 3 === 1))
+const isPowerOfFour = (n) => n > 0 && (n & (n - 1)) === 0 && n % 3 === 1
 
 export { isPowerOfFour }