feat: add vscode slice for message passing with extension

[heyzec]

Description

FYP: Source Academy as Visual Studio Code Extension

This PR makes the frontend's behavior change conditionally when it detects itself to be running as an iframe in the VS Code extension. This is required so that it can send and receive the editor text contents, encapsulated as messages, to the VS Code extension.

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

Checklist

• I have tested this code

[RichDom2185]

Hi, thanks for working on this! Could you update the test snapshots?

[coveralls]

Pull Request Test Coverage Report for Build 12947091999

Details

• 30 of 48 (62.5%) changed or added relevant lines in 9 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 31.22%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/commons/application/actions/VscodeActions.ts	1	2	50.0%
src/commons/application/reducers/VscodeReducer.ts	5	6	83.33%
src/features/vscode/messages.ts	9	15	60.0%
src/commons/application/Application.tsx	8	18	44.44%

Totals
Change from base Build 12903997600:	0.02%
Covered Lines:	4860
Relevant Lines:	14681

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💛 - Coveralls