highlight last-edit in the old docs

[kianenigma]

• if older than 1 year, yellow
• if older than 2 years, red.

Would be good if it becomes more visible, like at the top of the page.

and so on.

[Rashmirreddy]

We will include a banner like or something that gets immediate attention at the top of the pages once we create related topics in the master tutorial. Users can click the link to view the updated content. - https://github.com/paritytech/polkadot-sdk-docs/issues/26

There isn't much space to include the Last Edited tag at the top of the page. Closing this issue after discussing with @kianenigma.