Refactor neovim config file structure

All plugins are now in their own files with their lazy specifications
and configurations. Also moved lazy initialization to init.lua because
it is very compact now

home/.config/nvim/lua/plugins/asciidoc.lua

@@ -0,0 +1,13 @@
+-- AsciiDoc plugins are grouped together here
+return {
+  -- Vim ♥️ Asciidoctor
+  {
+    "habamax/vim-asciidoctor",
+    ft = { "asciidoctor", "asciidoc" },
+  },
+  -- AsciiDoc preview
+  {
+    "tigion/nvim-asciidoc-preview",
+    ft = { "asciidoctor", "asciidoc" },
+  },
+}