Update UserID Extraction Algorithm

[craigtrim]

{
   "blocks":[
      {
         "block_id":"4rdo",
         "text":{
            "text":"<@U045HCSMG8K> How long can particulate pollution remain airborne?",
            "type":"mrkdwn",
            "verbatim":false
         },
         "type":"section"
      }
   ],
   "channel":"C046DB9TLEL",
   "team":"T045AR44M70",
   "text":"<@U045HCSMG8K> How long can particulate pollution remain airborne?",
   "ts":1665724403.461959,
   "type":"app_mention",
   "user":"U046G4FURQT"
}

[craigtrim]

The blocks[text/text] pattern is new to the algorithm