Replaced custom Element class methods with native versions

[david-yz-liu]

Proposed Changes

(Describe your changes here. Also describe the motivation for your changes: what problem do they solve, or how do they improve the application or codebase? If this pull request fixes an open issue, use a keyword to link this pull request to the issue.)

This PR removes some old helper methods that were added to Element.prototype to handle classes, modelled after jQuery. With the standardization of Element.classList these methods aren't necessary and so I've switched to their native counterparts. This removes the need to load application.js.

Note that I've left instances of calling addClass/removeClass/hasClass in the codebase when they are called on jQuery objects.

Screenshots of your changes (if applicable)

Associated documentation repository pull request (if applicable)

Type of Change

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Type	Applies?
🚨 Breaking change (fix or feature that would cause existing functionality to change)
✨ New feature (non-breaking change that adds functionality)
🐛 Bug fix (non-breaking change that fixes an issue)
🎨 User interface change (change to user interface; provide screenshots)
♻️ Refactoring (internal change to codebase, without changing functionality)	X
🚦 Test update (change that only adds or modifies tests)
📦 Dependency update (change that updates a dependency)
🔧 Internal (change that only affects developers or continuous integration)

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Questions and Comments

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[coveralls]

Coverage Report for CI Build 25949828813

Coverage remained the same at 91.763%

Details

• Coverage remained the same as the base build.
• Patch coverage: 3 uncovered changes across 1 file (0 of 3 lines covered, 0.0%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
app/javascript/Components/Result/image_viewer.jsx	3	0	0.0%

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	48960
Covered Lines:	45672
Line Coverage:	93.28%
Relevant Branches:	1870
Covered Branches:	971
Branch Coverage:	51.93%
Branches in Coverage %:	Yes
Coverage Strength:	129.76 hits per line

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💛 - Coveralls