extract image in textnode

[unsleepy22]

fix the issue that images within text nodes are not extracted, which is not unusual in web pages.
i.e.,

<p><img src="aa.jpg"></img><p>

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.26%. Comparing base (4e59c8a) to head (e466953).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #757   +/-   ##
=======================================
  Coverage   99.26%   99.26%           
=======================================
  Files          21       21           
  Lines        3542     3559   +17     
=======================================
+ Hits         3516     3533   +17     
  Misses         26       26           

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[adbar]

Hi @unsleepy22, thanks for the PR. I still have questions about it (see above), could you please have a look?

[unsleepy22]

Hi @unsleepy22, thanks for the PR. I still have questions about it (see above), could you please have a look?

thanks for your comments, fixed and rebased my commits, would you take a look again?

[adbar]

LGTM, thanks.