Parse string `[SOURCE: ...]`

[Intelligent2013]

From https://github.com/metanorma/stepmod2mn/issues/179#issuecomment-2083273335.

The source XML (data\modules\reference_schema_for_sysml_mapping\module.xml):

 <definition>
     <term>ARM in SysML</term>
     <def>
        <p>
        application reference model transformed from EXPRESS to SysML
        </p>
        <p>
        [SOURCE: ISO/TS 10303-4000:2023, 3.1.1, Modified – Notes to entry removed]
        </p>
    </def>
 </definition>

The source paragraph should be parsed into:

[.source]
<<bibitem_ISO10303-4000,clause=3.1.1>>, Notes to entry removed