CLI: Update docs to v4

[anshumanv]

Feature to document
New CLI

Author(s)
Me

Additional information
A lot has changed in the CLI v4 since v3 hence this issue is to track updates to the new CLI docs.

/cc @evilebottnawi

• I am willing to work on this issue and submit a pull request.

[snitin315]

Main Highlights -

• Core flags
• Negated flags
• Multiple types fir stats -> --stats (means stats: true) , --stats verbose (means stats: verbose)
• Multiple entries --entry a.js --entry b.js
• --env flag
• --analyze
• out of box serve & info

[anshumanv]

We've touched almost everything in the new CLI, need full rewrite 😄

[anshumanv]

@snitin315 I think I've covered most from your list, can you go over again and see what we've missed?

[snitin315]

I think only the last point is left from the list.