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>

Graphs/test/BreadthFirstShortestPath.test.js

@@ -21,8 +21,19 @@ describe('BreadthFirstShortestPath', () => {
   */
 
   it('should return the visited nodes', () => {
-    expect(breadthFirstShortestPath(graph, 'C', 'E')).toEqual(['C', 'D', 'A', 'B', 'E'])
-    expect(breadthFirstShortestPath(graph, 'E', 'B')).toEqual(['E', 'D', 'A', 'B'])
+    expect(breadthFirstShortestPath(graph, 'C', 'E')).toEqual([
+      'C',
+      'D',
+      'A',
+      'B',
+      'E'
+    ])
+    expect(breadthFirstShortestPath(graph, 'E', 'B')).toEqual([
+      'E',
+      'D',
+      'A',
+      'B'
+    ])
     expect(breadthFirstShortestPath(graph, 'F', 'G')).toEqual(['F', 'G'])
     expect(breadthFirstShortestPath(graph, 'A', 'G')).toEqual([])
   })