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

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

String/MaxCharacter.js

@@ -5,7 +5,8 @@
  * @param {RegExp} ignorePattern - ignore the char in str that is not required
  * @returns {string} - char
  */
-const maxCharacter = (str, ignorePattern) => { // initially it's count only alphabets
+const maxCharacter = (str, ignorePattern) => {
+  // initially it's count only alphabets
   if (typeof str !== 'string') {
     throw new TypeError('Argument should be a string')
   } else if (!str) {