As of Umbraco 10, we've released the package under a new name. See the Limbo Textbox package instead.
Extended textbox and textarea property editors for Umbraco 8+.
To install in Umbraco 8:
Install-Package Skybrud.Umbraco.TextBox -Version 1.0.1
(or install the Umbraco package)
To install in Umbraco 9:
dotnet add package Skybrud.Umbraco.TextBox --version 2.0.4