Fix CSV Not Displayed on User Import

[chrtorres]

🗣 Description

• Fixed user CSV import not displaying on UI
• Added delete file function to remove unwanted CSV

💭 Motivation and context

Previously, users were able to select a CSV file to upload but no prompt or indication was provided to notify the user of the applied changes. In this fix, a selected CSV file will be displayed on the dashboard, accompanied by a delete button should you choose to change files. Once a user is satisfied with the selected file, an "Upload CSV" button has been added to confirm the changes being added to the database.

This closes issue #40

📷 Screenshots (if appropriate)

Before Fix:

After Fix:

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Create a release.

[Matthew-Grayson]

Looks great

[cduhn17]

LGTM

[rapidray12]

IAH ILF