Add Instagram share token parameter (stkn)

[GionLennon]

Adds stkn to the Instagram provider's rules array.

Instagram appends stkn to post URLs when shared via the native copy-link feature. This token is a tracking/share identifier and is not required to view the content.

Changes:
Only data.json was modified. The stkn parameter was added to the existing rules array for the instagram provider:

json
"rules": [
  "igshid",
  "igsh",
  "stkn"
]