docs: audits and updates the KEYS command doc

[swaingotnochill]

Resolves issue https://github.com/DiceDB/dice/issues/843

Audits and Changes:

• [x] Change the CLI prompt to 127.0.0.1:7379>
• [x] Markdown table for "parameters" and "return" values.
• [x] Run and check if the examples are working as expected.
• [x] Run and check if the examples give same output in redis.
• [x] Remove the conclusion in the end.

Other issues found during auditing:

1. https://github.com/DiceDB/dice/issues/851