doc: remove old instructions in README

README.md

@@ -1,28 +1 @@
 # zsh-setup for sup39
-## Usage
-### Full setup
-```zsh
-curl https://raw.githubusercontent.com/sup39/zsh-setup/master/setup.sh | sh -
-source $HOME/.zshrc
-```
-Alternatively, use the shortened url:
-```zsh
-# Download setup file and execute it
-curl -sL link.sup39.dev/zsh-setup | sh -
-
-# Finally, source the zshrc file
-source $HOME/.zshrc
-```
-
-### zshrc only
-```zsh
-curl https://raw.githubusercontent.com/sup39/zsh-setup/master/zshrc >> $HOME/.zshrc
-source $HOME/.zshrc
-```
-
-## Content
-- `~/.zshenv`
-- `~/.zshrc`
-- `~/.screenrc`
-
-:bulb: No overwriting if exists