WIP code for directory picker on PWA's

[chrisekelley]

using File System Access API.
Imported the @types/wicg-file-system-access types to enable use of this API; may not be necessary in the future.

Description

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[What is the business, user experience or technical problem? What is the motivation or context? Any Dependencies required for the change? e.g tangy-forms version etc]
[List the issues fixed and any other relevant issues]

• Fixes #IssueNumber

Type of Change

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• 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

Proposed Solution

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Limitations and Trade-offs

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Security considerations

Screenshots/Videos

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Tests

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[How you tested (or have not tested) this PR and what where those steps.]

Notices, Regressions, Breaking Changes

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TODOS/enhancements

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• [Develop more tests for this PR.]
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