add link to tracker swagger docs

[robcxyz]

Adding link to the swagger docs that feed the tracker. Several people in the community are using these so they should be documented here as well.

[han-so1omon]

@robcxyz I would prefer that this goes into a different page, as it would be difficult for people to find it as proposed currently. Something like the following (based on the Ethereum docs):

• New pages @ ICON Stack -> Data and analytics -> Block explorers
• Data and analytics page similar to this one (with appropriate sections)
• Block explorers page similar to this one. This is where the API links should go