implement file type icons

[mhsh312]

Fixes #2542 (needs discussion about icon design)

Changes:

Added File Type Icons.

I have created a new React Component and passed the file extension as a prop. The component returns suitable icon according to the prop. I have not put much thought into choosing the icons (I have used react-icons) as the icon choice can be reviewed and discussed later. For the file types I could not find the icons for, I have set the default case to the old generic FileIcon.

I have verified that this pull request:

• [x] has no linting errors (npm run lint)
• [x] has no test errors (npm run test)
• [x] is from a uniquely-named feature branch and is up to date with the develop branch.
• [x] is descriptively named and links to an issue number, i.e. Fixes #123

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