completely refactor and modularize flake

modules/default/common/nixvim/neotree.nix

@@ -0,0 +1,42 @@
+{ ... }:
+{
+  programs.nixvim = {
+    plugins = {
+      neo-tree = {
+        enable = true;
+        sources = ["filesystem" "buffers" "git_status" "document_symbols"];
+        addBlankLineAtTop = false;
+
+        filesystem = {
+          bindToCwd = false;
+          followCurrentFile = {
+            enabled = true;
+          };
+        };
+
+        defaultComponentConfigs = {
+          indent = {
+            withExpanders = true;
+            expanderCollapsed = "󰅂";
+            expanderExpanded = "󰅀";
+            expanderHighlight = "NeoTreeExpander";
+          };
+
+          gitStatus = {
+            symbols = {
+              added = " ";
+              conflict = "󰩌 ";
+              deleted = "󱂥";
+              ignored = " ";
+              modified = " ";
+              renamed = "󰑕";
+              staged = "󰩍";
+              unstaged = "";
+              untracked = " ";
+            };
+          };
+	};
+      };
+    };
+  };
+}