Readme.md: Add RHEL to linux installation hints

Change-Id: I61976a3a861b57a777ca1dcaeb3b0f534102899f
diff --git a/Readme.md b/Readme.md
index b07d891..7b23d8e 100644
--- a/Readme.md
+++ b/Readme.md
@@ -24,10 +24,10 @@
 #### Debian / Ubuntu
 sudo apt install r-base-dev libcurl4-gnutls-dev libxml2-dev libsodium-dev
 
-#### Fedora / CentOS >= 8
+#### Fedora / CentOS >= 8 / RHEL >= 8
 sudo dnf install R-devel libcurl-devel openssl-devel libxml2-devel libsodium-devel
 
-#### CentOS < 8
+#### CentOS < 8 / RHEL < 8
 sudo yum install R-devel libcurl-devel openssl-devel libxml2-devel libsodium-devel
 
 #### Arch Linux