neovim: setup snippets & remove friendly snippets plugin

neovim/.config/nvim/snippets/go.lua

@@ -0,0 +1,15 @@
+---@diagnostic disable:undefined-global
+
+return {
+  s(
+    { trig = "iferr", snippetType = "autosnippet" },
+    fmta(
+      [[
+    if err != nil {
+        return <>
+    }
+    ]],
+      { i(0) }
+    )
+  ),
+}