Show related (similar/alternative) apps

### Proposal

In the detail view of an app: Show apps that are related to the app (Plugins, based on, etc.).

**Related Apps**
One way to implement this is based on the topics in github. Some related apps has as topic of an other app (or library). eg. https://github.com/topics/josm
Use framework prop in software template

**Similar apps, You might also be interested in, Free alternatives**
Find similar apps based on genre, features (ignore propertary software), Topics, (include Platform filter), sort result by, most genre found, then by most features, topics, (pre sorted by score and language), show 3 of them

### Links / references / screenshots
- #37

Start with the app detail view and the software template, using issue #37 as the related reference. Determine how GitHub topics, framework, genre, features, platforms, and language scores are represented before defining the related-app rules. Done means the detail view shows the requested related, similar, and free-alternative results with the stated filtering and ordering.

Written by the indexing model from the issue text.