docs: Add sample vault, for use in screenshots for the documentation

[claremacrae]

Description

• Add vault for docs, in resources/sample_vaults/Tasks-Demo/
• It has a few settings saved, for creating readable screenshots
• The workspace file is ignored by git
• The Tasks plugin is installed and enabled ("1.7.0")

Motivation and Context

• I wish to regenerate the current screenshots on a white background, to attempt to make their text legible

How has this been tested?

• By opening the vault on my Mac

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Refactor (non-breaking change which only improves the design or structure of existing code, and making no changes to its external behaviour)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• For documentation

Checklist:

• My code follows the code style of this project and passes yarn run lint.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• My change has adequate Unit Test coverage.

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