feat: adding maintenance label

[aorumbayev]

Description

Please explain the changes you made here

• Adding env var to toggle maintenance view

Checklist

Please, make sure to comply with the checklist below before expecting review

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary

[codecov]

Codecov Report

Merging #15 (f778370) into main (56ccdd3) will decrease coverage by 0.10%.
The diff coverage is 8.33%.

@@            Coverage Diff             @@
##             main      #15      +/-   ##
==========================================
- Coverage   27.07%   26.96%   -0.11%     
==========================================
  Files          88       89       +1     
  Lines        1555     1565      +10     
  Branches      137      139       +2     
==========================================
+ Hits          421      422       +1     
- Misses       1125     1134       +9     
  Partials        9        9              

Impacted Files	Coverage Δ
src/components/Headers/NavBar.tsx	56.39% <ø> (ø)
src/components/Layouts/MaintenanceLayout.tsx	0.00% <0.00%> (ø)
src/pages/leaderboard.page.tsx	0.00% <0.00%> (ø)
src/pages/packs.page.tsx	0.00% <0.00%> (ø)
src/common/constants.ts	79.54% <50.00%> (-1.41%)	⬇️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[github-actions]

Deploy preview for algoworld-explorer ready!

✅ Preview
https://algoworld-explorer-8b332endy-algoworldexplorer.vercel.app
https://pr15-28.vercel-action.millionalgos.com

Built with commit d613b11.
This pull request is being automatically deployed with vercel-action