Updated readme.md to include SPFx 1.5.1 (SharePoint#2163)

Author: hugoabernier

README.md

@@ -15,6 +15,9 @@ We’ll also monitor [#spfx](http://sharepoint.stackexchange.com/tags/spfx/), [#
 You can also tweet / follow [@officedev](https://twitter.com/officedev) or [@officedevpnp](https://twitter.com/officedevpnp).
 
 ## SharePoint Framework Releases
+* **June 26, 2018**
+   * **SPFx v1.5.1** - [See the release notes here](https://github.com/SharePoint/sp-dev-docs/wiki/Release-Notes-for-SPFx-Package-Version-1.5.1)
+   
 * **June 5, 2018**
    * **SPFx v1.5** - [See the release notes here](https://github.com/SharePoint/sp-dev-docs/wiki/Release-Notes-for-SharePoint-Framework-Package-v1.5)