* chore: renderer test coverage
* fix: lint
* chore: api tests
* chore: tests for app reducer and StartGradeButton
* chore: lint
* fix: update reducer tests
* chore: more test coverage
* chore: test coverage
* chore: update test for merge conflicts
* fix: response display to show medium size on even the content isn't big enough
* fix: don't show download button when there isn't submission files
* feat: additional default support file for image renderer
* feat: add file renderer that support common error handling and loading banner
* chore: use axios instead of get from utils
* chore: fixed typo and update snapshots
