Updating Cypress readme + adding note about exposed queryClient

[olemartinorg]

Description

• The Studio team will start using our exposed queryClient to make their preview refresh faster: Remove full reload of preview altinn-studio#12517
  • I'm adding a comment about this in our code, to make sure we don't just remove the queryClient (and break preview in Studio).
• Refreshing the Cypress README.md to reflect the way I've been running Cypress for (pretty much) ever. The cy:... scripts probably worked fine on windows, and they're nice if you're just running all the tests always, but giving people the power of just running npx cypress ... will give them greater flexibility.
• Removing dependencies only used for making these scripts cross-platform(!), which are not otherwise used in our project.

Related Issue(s)

• Adapt app-frontend-react to accept reload commands from Studio #1088
• Remove full reload of preview altinn-studio#12517
• Fixes for flaky tests, separate configs for docker/podman #1919

Verification/QA

• Manual functionality testing
  • I have tested these changes manually
  • Creator of the original issue (or service owner) has been contacted for manual testing (or will be contacted when released in alpha)
  • No testing done/necessary
• Automated tests
  • Unit test(s) have been added/updated
  • Cypress E2E test(s) have been added/updated
  • No automatic tests are needed here (no functional changes/additions)
  • I want someone to help me make some tests
• UU/WCAG (follow these guidelines until we have our own)
  • I have tested with a screen reader/keyboard navigation/automated wcag validator
  • No testing done/necessary (no DOM/visual changes)
  • I want someone to help me perform accessibility testing
• User documentation @ altinn-studio-docs
  • Has been added/updated
  • No functionality has been changed/added, so no documentation is needed
  • I will do that later/have created an issue
• Support in Altinn Studio
  • Issue(s) created for support in Studio
  • This change/feature does not require any changes to Altinn Studio
• Sprint board
  • The original issue (or this PR itself) has been added to the Team Apps project and to the current sprint board
  • I don't have permissions to do that, please help me out
• Labels
  • I have added a kind/* label to this PR for proper release notes grouping
  • I don't have permissions to add labels, please help me out

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud