[ofiwg] Release candidates available for v1.20.1, v1.19.1, and v1.18.3

[Xiong, Jianxin]

The release candidates for the upcoming v1.20.1, v1.19.1, and v1.18.3 releases are now available. 
Here are the download links:

https://github.com/ofiwg/libfabric/releases/tag/v1.20.1rc1
https://github.com/ofiwg/libfabric/releases/tag/v1.19.1rc1
https://github.com/ofiwg/libfabric/releases/tag/v1.18.3rc1

The GA releases are expected to be available in about a week.

-Jianxin