UID2-6592: Document UID2 token validator in integration guides

[BehnamMozafari]

• Added new reference page "UID2 Token Validator" giving an overview and instructions
• Linked to reference page in "Preparing DII for Processing" section of integration guides
• Linked to tool reference page in "Normalization and Encoding"

[genwhittTTD]

Looks good! Few small edits and I sent the proposed updates to the sidebars file via Slack.

Great work.

[genwhittTTD]

Few more small edits.
And then there is one more thing... I built both languages and there are errors in the Japanese, as I'd suspected there would be, because you're adding new content.
If you could just address these few edits please, I'll check in the Japanese updates and you'll be good to go.