CLI command added for "lb4 cache --config"

[sohaibahsan007]

lb4 cache command generates the code required to add cache capabilities in a loopback 4 application. The command prompts the user for a valid datasource with kv-redis connector. It then generates a cache model, repository, and cache-strategy provider. It also updates application.ts to add CacheComponent and bind CacheStrategyProvider. It then prints a message telling the user to add some lines of code to sequence for caching to work. We cannot auto-generate this code, because sequence can vary in different implementations in many applications. So it would be difficult to add code in the right place.

Checklist

• DCO (Developer Certificate of Origin) signed in all commits
• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• Code conforms with the style guide
• API Documentation in code was updated
• Documentation in /docs/site was updated
• Affected artifact templates in packages/cli were updated
• Affected example projects in examples/* were updated