Merge pull request nvim-lua#480 from dam9000/pr-faq-appname

README.md: add a note about NVIM_APPNAME in the FAQ section

Author: melobern

README.md

@@ -149,6 +149,13 @@ Each PR, especially those which increase the line count, should have a descripti
   * You should back it up, then delete all files associated with it.
   * This includes your existing init.lua and the neovim files in `~/.local` which can be deleted with `rm -rf ~/.local/share/nvim/`
   * You may also want to look at the [migration guide for lazy.nvim](https://github.com/folke/lazy.nvim#-migration-guide)
+* Can I keep my existing configuration in parallel to kickstart?
+  * Yes! You can use [NVIM_APPNAME](https://neovim.io/doc/user/starting.html#%24NVIM_APPNAME)`=nvim-NAME` to maintain multiple configurations. For example you can install the kickstart configuration in `~/.config/nvim-kickstart` and create a script `~/bin/nvim-kickstart`:
+    ```
+    #!/bin/sh
+    exec env NVIM_APPNAME=nvim-kickstart nvim "$@"
+    ```
+    When you run Neovim with `nvim-kickstart` it will use the alternative config directory and the matching local directory: `~/.local/share/nvim-kickstart`. You can apply this approach to any Neovim distribution that you would like to try out.
 * What if I want to "uninstall" this configuration:
   * See [lazy.nvim uninstall](https://github.com/folke/lazy.nvim#-uninstalling) information
 * Are there any cool videos about this plugin?