feat: allow strings for pluginSpec config via mkLuaInline

[nekowinston]

Just occurred to me that toLua allows us to use mkLuaInline for short configs:

   vim-dadbod-ui = {
     src = srcs.vim-dadbod-ui;
-    # TODO: config file with:
-    # vim.g.db_ui_use_nerd_fonts = true
-    # vim.g.db_ui_win_position = "right"
+    config = lib.generators.mkLuaInline ''
+      function()
+        vim.g.db_ui_use_nerd_fonts = true
+        vim.g.db_ui_win_position = "right"
+      end
+    '';
   };

I'm not sure if the current isLuaInline is optimal? Sadly, generators.nix doesn't export it (and also expects an attrset, so it fails when encountering paths).

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Alternatively, we could also allow string types and then call mkLuaInline in {isString attrs.config) {...}?

[willruggiano]

Probably just use strings, and then call mkLuaInline internally as you say