Upgrade syntax support for Typescript 4.2.3

[s-khuntia]

Please upgrade typescript to support @typescript-eslint/typescript-estree so we can prevent the warning

WARNING: You are currently running a version of TypeScript which is not officially supported by @typescript-eslint/typescript-estree.

You may find that it works just fine, or you may not.

SUPPORTED TYPESCRIPT VERSIONS: >=3.3.1 <4.2.0

YOUR TYPESCRIPT VERSION: 4.2.3

Please only submit bug reports when using the officially supported version.

REFERENCING SIMILAR ISSUE

#489

[rchl]

Was fixed in #563 (not released yet at the time of writing this comment).