* Update README.md
Add tags file generation instruction.
* Update lsp.txt
$ mkdir -p $HOME/.vim/pack/downloads/opt
$ cd $HOME/.vim/pack/downloads/opt
$ git clone https://github.com/yegappan/lsp
+$ vim -u NONE -c "helptags $HOME/.vim/pack/downloads/opt/lsp/doc" -c q
```
After installing the plugin using the above steps, add the following line to
$ mkdir -p $HOME/.vim/pack/downloads/opt
$ cd $HOME/.vim/pack/downloads/opt
$ git clone https://github.com/yegappan/lsp
+ $ vim -u NONE -c "helptags $HOME/.vim/pack/downloads/opt/lsp/doc" -c q
or you can use any one of the Vim plugin managers (dein.vim, pathogen, vam,
vim-plug, volt, Vundle, etc.) to install and manage this plugin.