feat: implement export page

[kyrylo-kh]

• Implemented new page - Export page
• Created new generic component - CourseStepper (also will be used in import page)

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[codecov]

Codecov Report

Patch coverage: 95.95% and project coverage change: +0.35% 🎉

Comparison is base (a1793ef) 84.55% compared to head (74a9a37) 84.91%.
Report is 8 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #586      +/-   ##
==========================================
+ Coverage   84.55%   84.91%   +0.35%     
==========================================
  Files         307      330      +23     
  Lines        4993     5296     +303     
  Branches     1102     1165      +63     
==========================================
+ Hits         4222     4497     +275     
- Misses        747      753       +6     
- Partials       24       46      +22     

Files Changed	Coverage Δ
src/CourseAuthoringRoutes.jsx	100.00% <ø> (ø)
src/store.js	100.00% <ø> (ø)
src/export-page/data/thunks.js	82.85% <82.85%> (ø)
src/export-page/export-stepper/ExportStepper.jsx	96.00% <96.00%> (ø)
src/export-page/CourseExportPage.jsx	96.15% <96.15%> (ø)
src/export-page/data/api.js	100.00% <100.00%> (ø)
src/export-page/data/constants.js	100.00% <100.00%> (ø)
src/export-page/data/selectors.js	100.00% <100.00%> (ø)
src/export-page/data/slice.js	100.00% <100.00%> (ø)
src/export-page/export-footer/ExportFooter.jsx	100.00% <100.00%> (ø)
... and 10 more

... and 44 files with indirect coverage changes

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[e0d]

Hi @Thposbsmt it looks like this PR reduces coverage, can you have a look?

[KristinAoki]

What was the reasoning for use redux to control the state of the visibility of the error modal versus useToggle from paragon

[kyrylo-kh]

Redux allow to change state anywhere. In this case isErrorModalOpen changes in thunks and ExportModalError.jsx. We cannot do it with useToggle

[sundasnoreen12]

There is a UI glitch on the MFE because of adding custom css for this paragon class "pgn__stepper-header-step-list ".
I added the fix in this PR. Please review again at your end and let me know is the provided fix is also working fine at your end.
@KristinAoki

[openedx-webhooks]

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