ci: add macOS 11 Big Sur

Remove all traces of Travis CI

Change-Id: Ie9ad527af4921c4f3c56903851200131ed0d5e87
diff --git a/docs/INSTALL.rst b/docs/INSTALL.rst
index a326ff3..ba4a2a9 100644
--- a/docs/INSTALL.rst
+++ b/docs/INSTALL.rst
@@ -9,18 +9,21 @@
 
 -  Ubuntu 18.04 (amd64, armhf, i386)
 -  Ubuntu 20.04 (amd64)
--  macOS 10.13
--  macOS 10.14
+-  Ubuntu 21.04 (amd64)
 -  macOS 10.15
+-  macOS 11 (Intel only)
 -  CentOS 8
 
 NFD is known to work on the following platforms, although they are not officially
 supported:
 
--  Debian 10 (Buster)
+-  Alpine >= 3.12
+-  Debian >= 10
 -  Fedora >= 29
 -  Gentoo Linux
--  Raspbian >= 2019-06-20 (Buster)
+-  Raspberry Pi OS (formerly Raspbian) >= 2019-06-20
+-  macOS 10.13
+-  macOS 10.14
 
 .. _Install NFD on Ubuntu Linux using the NDN PPA repository: