Add content in README.md as per README.md format.

Verified the MR9, the readme.md file is updated as per standard but the patch is not cleanly applied:

9.patch:117: trailing whitespace.
The module provides /health endpoint which is never cached and returns only
9.patch:118: trailing whitespace.
timestamp as a body with HTTP status code 200. If Drupal fails to bootstrap,
9.patch:120: trailing whitespace.
something wrong with the particular instance and can drop it from load
warning: README.md has type 100644, expected 100755
warning: README.md has type 100644, expected 100755
warning: README.md has type 100644, expected 100755
warning: 3 lines add whitespace errors.

Merged to 3.x. Thank you for the MR!