Updates to the README.md

[fruch]

@tzach @annastuchlik

Any input on what you guys would expect with this tool documentation (i.e. README.md)

[tzach]

• Should include wording on Scylla Cloud connectivity (can be added later)
• Need to use the same license as upstream (Apache Cassandra)

[fruch]

• Should include wording on Scylla Cloud connectivity (can be added later)
• Need to use the same license as upstream (Apache Cassandra)

Added license information

[tzach]

LGTM