Add custom field in system Configuration in magento 2

I have tried to add new field in System configuration in magento 2. I have used the below code, but I am getting this error:

Could not create an acl object: Invalid XML in file path/to/file

Suggest me the correct way to do this. Thanks in advance!!

acl.xml

<?xml version="1.0"?>
<!--
/**
 * Location: magento2_root/app/code/Namespace/Module/etc/acl.xml
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <acl>
        <resources>
            <resource id="Magento_Backend::admin">
                <resource id="Magento_Backend::stores">
                    <resource id="Magento_Backend::stores_settings">
                        <resource id="Magento_Config::config">
                            <resource id="NAmespace_Module::config" title="Custom Settings" sortOrder="50" />
                        </resource>
                    </resource>
                </resource>
            </resource>
        </resources>
    </acl>

system.xml

<?xml version="1.0"?>
<!--
/**
 * Location: magento2_root/app/code/Namespace/Module/etc/adminhtml/system.xml
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <system>
        <tab id="settings" translate="label" sortOrder="1000">
            <label>Settings</label>
        </tab>
        <section id="example_section" translate="label" type="text" sortOrder="100" showInDefault="1" showInWebsite="1" showInStore="1">
            <label>Example config section</label>
            <tab>settings</tab>
            <resource>Namespace_Module::config</resource>
            <group id="general" translate="label" type="text" sortOrder="10" showInDefault="1" showInWebsite="1" showInStore="1">

                <field id="facebook" translate="label" type="text" sortOrder="20" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Facebook</label>
                </field>

                <field id="textarea_example" translate="label" type="textarea" sortOrder="50" showInDefault="1" showInWebsite="1" showInStore="1">
                    <label>Textarea example</label>
                </field>
            </group>
        </section>
    </system>
</config>