doc

- develop.txt is for design/guidelines; architecture/concepts should
  live elsewhere (currently src/nvim/README.md)
- move dev-jargon to intro.txt
- replace https://neovim.io/community (deprecated) with
  https://neovim.io/#chat
- <Cmd> avoids CmdlineEnter/Leave
  https://github.com/vim/vim/issues/2889

src/nvim/version.c

@@ -2173,7 +2173,7 @@ void intro_message(int colon)
     N_(NVIM_VERSION_LONG),
     "",
     N_("Nvim is open source and freely distributable"),
-    N_("https://neovim.io/community"),
+    N_("https://neovim.io/#chat"),
     "",
     N_("type  :help nvim<Enter>       if you are new! "),
     N_("type  :checkhealth<Enter>     to optimize Nvim"),