Updated README to include snapshot command
Summary:
* Added text for `below snapshot` command
* Fixed below logo in readme
Pull Request resolved:
-![below](https://github.com/facebookincubator/below/main/img/below_logo_horizontal.png)
+![below](https://github.com/facebookincubator/below/blob/main/img/below_logo_horizontal.png)
[![CI](https://github.com/facebookincubator/below/workflows/CI/badge.svg)](https://github.com/facebookincubator/below/actions?query=workflow%3ACI+branch%3Amain+)
[![Matrix chat](https://img.shields.io/matrix/below:matrix.org)](https://matrix.to/#/#below:matrix.org)
@@ -14,6 +14,7 @@ has support for:
* `replay` mode to replay historical system data
* `live` mode to view live system data
* `dump` subcommand to report script-friendly information (eg JSON and CSV)
+* `snapshot` subcommand to create a replayable snapshot file of historical system data
below does **not** have support for cgroup1.
