fix(icon_config): don't ignore git_icons user configuration

[kawaemon]

I found out that the current implementation ignores git icons configuration by users. The diff below fixes this issue, but I used the built-in function vim.tbl_deep_extend in this PR because it is simple and prevents this kind of easy miss.

diff --git a/lua/nvim-tree/renderer/icon-config.lua b/lua/nvim-tree/renderer/icon-config.lua
index e6d8cfd..9990afb 100644
--- a/lua/nvim-tree/renderer/icon-config.lua
+++ b/lua/nvim-tree/renderer/icon-config.lua
@@ -35,7 +35,7 @@ function M.get_config()
     if user_icons.symlink then
       icons.symlink = user_icons.symlink
     end
-    for key, val in pairs(user_icons.git or {}) do
+    for key, val in pairs(user_icons.git_icons or {}) do
       if icons.git_icons[key] then
         icons.git_icons[key] = val
       end

[kawaemon]

looks like this issue will be fixed by #1279. never mind.