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/test/FindLcm.test.js

@@ -2,16 +2,24 @@ import { findLcm, findLcmWithHcf } from '../FindLcm'
 
 describe('findLcm', () => {
   it('should throw a statement for values less than 1', () => {
-    expect(() => { findLcm(0, 0) }).toThrow(Error)
+    expect(() => {
+      findLcm(0, 0)
+    }).toThrow(Error)
   })
 
   it('should throw a statement for one value less than 1', () => {
-    expect(() => { findLcm(1, 0) }).toThrow(Error)
-    expect(() => { findLcm(0, 1) }).toThrow(Error)
+    expect(() => {
+      findLcm(1, 0)
+    }).toThrow(Error)
+    expect(() => {
+      findLcm(0, 1)
+    }).toThrow(Error)
   })
 
   it('should return an error for values non-integer values', () => {
-    expect(() => { findLcm(4.564, 7.39) }).toThrow(Error)
+    expect(() => {
+      findLcm(4.564, 7.39)
+    }).toThrow(Error)
   })
 
   it('should return the LCM of two given integers', () => {
@@ -21,16 +29,24 @@ describe('findLcm', () => {
 
 describe('findLcmWithHcf', () => {
   it('should throw a statement for values less than 1', () => {
-    expect(() => { findLcmWithHcf(0, 0) }).toThrow(Error)
+    expect(() => {
+      findLcmWithHcf(0, 0)
+    }).toThrow(Error)
   })
 
   it('should throw a statement for one value less than 1', () => {
-    expect(() => { findLcmWithHcf(1, 0) }).toThrow(Error)
-    expect(() => { findLcmWithHcf(0, 1) }).toThrow(Error)
+    expect(() => {
+      findLcmWithHcf(1, 0)
+    }).toThrow(Error)
+    expect(() => {
+      findLcmWithHcf(0, 1)
+    }).toThrow(Error)
   })
 
   it('should return an error for values non-integer values', () => {
-    expect(() => { findLcmWithHcf(4.564, 7.39) }).toThrow(Error)
+    expect(() => {
+      findLcmWithHcf(4.564, 7.39)
+    }).toThrow(Error)
   })
 
   it('should return the LCM of two given integers', () => {