Fix links in documentation

### Edit existing content 📝

**What do you think should be changed?**

The following links need to fixed:
- Link to the ransomware README (file path) on the ransomware simulation page
- Link to the READMEs (file extensions) on the development setup page
- Link to [cryptomining blog post](https://www.akamai.com/blog/security/operation-prowli-traffic-manipulation-cryptocurrency-mining) on network breach page
- Link for "Getting up and running" (syntax for linking) on the contributing index page
- Link to our roadmap (outdated, closed, read-only GitHub project) on the contributing index page