List entries look like:

*       text
1.      text
[label] text
label:: text

Flag it as a list entry, and work out the indent for subsequent lines

/^(
  (  \*          (?# bullet)
    |-           (?# bullet)
    |\d+\.       (?# numbered )
    |[A-Za-z]\.  (?# alphabetically numbered )
  )
  \s+
)\S/x