Add nvim to test

.travis.yml

@@ -1,6 +1,11 @@
 dist: focal
 
 language: minimal
+  
+before_install: 
+  - sudo add-apt-repository ppa:neovim-ppa/stable -y
+  - sudo apt-get update
+  - sudo apt-get -y install neovim
 
 install:
   - git clone https://github.com/leafOfTree/test ../test --depth=1