scripts: check_site: add need_number_range check

.luacheckrc

@@ -32,6 +32,7 @@ files["package/**/check_site.lua"] = {
 		"need_chanlist",
 		"need_domain_name",
 		"need_number",
+		"need_number_range",
 		"need_one_of",
 		"need_string",
 		"need_string_array",

scripts/check_site.lua

@@ -289,6 +289,19 @@ function M.need_number(path, required)
 	return need_type(path, 'number', required, 'be a number')
 end
 
+function M.need_number_range(path, min, max, required)
+	local val = need_type(path, 'number', required)
+	if not val then
+		return nil
+	end
+
+	if val < min or val > max then
+		var_error(path, val, "be in range [" .. min .. ", " .. max .. "]")
+	end
+
+	return val
+end
+
 function M.need_boolean(path, required)
 	return need_type(path, 'boolean', required, 'be a boolean')
 end