Failed to install "unknown package" from github

[MJimitater]

Tried to run languageserver_install(), but I get the error

> languageserver_install()
This will attempt to use:
source('https://install-github.me/REditorSupport/languageserver')
to install REditorSupport/languageserver into:
C:\Users\xxxxx\Documents/languageserver-library
All dependencies will also be installed there
! The directory C:\Users\xxxxx\Documents/languageserver-library will be RECURSIVELY REMOVED !
Do you agree?
(yes/No/abbrechen) yes
The install-github.me service is deprecated, please stop using it.
Fehler: Failed to install 'unknown package' from GitHub:
  cannot open URL 'https://api.github.com/repos/REditorSupport/languageserver/contents/DESCRIPTION?ref=master'

Whats wrong? Thanks in advance for any help