Improve the 404 page to match scigateway #1237

[joshuadkitenge]

Description

• Create pageNotFound
• Apply for all 404 pages

Testing instructions

Add a set up instructions describing how the reviewer should test the code

• Review code
• Check Actions build
• Review changes to test coverage
• {more steps here}

Agile board tracking

closes #1237

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.11%. Comparing base (05dad65) to head (c886478).
Report is 14 commits behind head on develop.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop    #1238    +/-   ##
=========================================
  Coverage    99.11%   99.11%            
=========================================
  Files           96       97     +1     
  Lines        17563    17610    +47     
  Branches      2994     2184   -810     
=========================================
+ Hits         17408    17455    +47     
  Misses         154      154            
  Partials         1        1            

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[joelvdavies]

Single comment, looks good.