Add file input

[tinykite]

What this does

Adds a new component, FileInput, to provide a file chooser that allows users to choose a file to upload as part of their own static archive.

Implementation Requirements

Main Goals:

• Add a reusable component that accepts a file in the formats of .gif, .jpg, .pdf, and .png
• The component will be used in the archive upload component, and look like this:

• Reuse as much existing HTML and CSS as possible
• Rewrite file handling logic using modern JavaScript
• File validation (to check if the file is larger than 100MB) will be handled by the backend
• If an error exists, it can be passed to the component and displayed in a way that matches the above screenshot

Screenshots

File chosen

Note: The visible, stringified File object shown above the screenshot is for debugging purposes only

File validation error

How to Test

• Try to choose a file. Only valid file formats should be selectable in the file input UI.
• Try to toggle input errors. The chosen file should still be visible, for now. (It shouldn't be overwritten)
• Try to reset the input errors.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 69.01%. Comparing base (ad6fcd7) to head (7c6fcc9). Report is 32 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #3545 +/- ## =========================================== - Coverage 69.23% 69.01% -0.22% =========================================== Files 48 48 Lines 6816 6842 +26 =========================================== + Hits 4719 4722 +3 - Misses 2097 2120 +23 ```

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