[Enhancement] Add a section for Specify the License

[Felix-Dynamsoft]

On DLR, we have a section for "Specify the License" so that we can attach a tracker on the link.
This link is mainly used for more information for the users where we initialize the license in sample.

For DDN, we should include this section to Specify the License so DDN samples can reference it!

DLR link: https://www.dynamsoft.com/label-recognition/programming/javascript/user-guide.html?ver=latest&utm_source=samples#specify-the-license

DDN link: https://www.dynamsoft.com/document-normalizer/docs/web/programming/javascript/user-guide/index.html#run-the-example

DBR also has it: https://www.dynamsoft.com/barcode-reader/programming/javascript/user-guide/?ver=10.2.10&utm_source=samples#specify-the-license

Eg.

/** LICENSE ALERT - README
 * To use the library, you need to first specify a license key using the API "initLicense" as shown below.
 */
Dynamsoft.License.LicenseManager.initLicense("DLS2eyJvcmdhbml6YXRpb25JRCI6IjIwMDAwMSJ9");
/**
 * You can visit https://www.dynamsoft.com/customer/license/trialLicense/?product=cvs&utm_source=samples&package=js to get your own trial license good for 30 days.
 * Note that if you downloaded this sample from Dynamsoft while logged in, the above license key may already be your own 30-day trial license.
 * For more information, see https://www.dynamsoft.com/label-recognition/programming/javascript/user-guide.html?ver=latest&utm_source=samples#specify-the-license or contact support@dynamsoft.com.
 * LICENSE ALERT - THE END
 */