Migrating 'Thumbnail' component

**path to the component**

- /src/atoms/Thumbnail.js

**DoD**

- convert the file to .ts extension
- define an interface for props in the component
- define an interface for internally used states (if any)
- define types for variables (if any)

Contribution steps can be found - [https://github.com/99xt/first-born/wiki/Migrating-to-TypeScript](https://github.com/99xt/first-born/wiki/Migrating-to-TypeScript)

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Start with /src/atoms/Thumbnail.js and the linked TypeScript migration guide. Inspect the component's props, internal state, and variables, then convert the file to .ts and define the requested interfaces and types. Done means the component is represented in TypeScript with all applicable props, state, and variables typed.

Written by the indexing model from the issue text.