Enable harper for only certain paths

gistfile1.txt

	root_dir = function(bufnr, on_dir)
		local fname = vim.api.nvim_buf_get_name(bufnr)
		local path = vim.loop.fs_realpath(fname)
		if not path then
			return nil
		end

		local allowed_dirs = {
			vim.loop.fs_realpath(vim.fn.expand("~/wiki/math")),
			vim.loop.fs_realpath(vim.fn.expand("~/wiki/physics")),
			vim.loop.fs_realpath(vim.fn.expand("~/wiki/programming")),
		}

		for _, dir in ipairs(allowed_dirs) do
			if dir and path:sub(1, #dir) == dir then
				on_dir(dir)
			end
		end
	end,