Bump Phaser from v3.55.2 to v3.87.0

[JustATin555]

Description

• Bump Phaser from 3.55.2 to 3.87.0 and address any breaking changes
• Add path as explicit dev dependency as Phaser 3.87.0 no longer lists it
• Add phaser3spectorjs to satisfy Phaser 3.87.0 undeclared dependency (unknown problem with Phaser's build process)
• Add a guard for undefined scene.input.mouse or scene.input.keyboard when disabled in config
• Add a try/catch to ensure missing background music assets do not cause fatal errors in Game
• Add a new .env variable, REACT_APP_USE_EMPTY_ASSET_PREFIX, which controls whether or not toS3Path() uses an asset prefix provided by the backend when loading images / sprites
• Silenced fatal error from ParserValidator when loading checkpoint into GameSimulator due to missing "galactic-harmony" when "galactic-harmony" does in fact exist (temporary)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Code quality improvements

How to test

• Tested with yarn test, all test cases passed
• Tested with yarn start, Source Academy launches and mock story chapters load properly
• Tested with actual story chapters

Checklist

• I have tested this code
• I have updated the documentation

[coveralls]

Pull Request Test Coverage Report for Build 13453702289

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 31.111%

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Totals
Change from base Build 13448387272:	0.0%
Covered Lines:	4870
Relevant Lines:	14776

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💛 - Coveralls

[RichDom2185]

Supersedes #3087

[JustATin555]

Marked as draft while checking if chapter errors are due to backend setup or the phaser upgrade.

[JustATin555]

A deeper look found that errors were coming from a failure to load assets from S3 bucket, likely caused by lack of read access.