[doc] Some examples in Part IV lack codeexample info

[muzimuzhi]

Version: 3.1.5b

• All examples in Sec. 28.3 Padding and Node Distances, pp. 422--425.
  Corresponding source file: Distances.lua
• Sec. 28.4--28.7.3, pp. 426--436, 439--440
• Sec. 28.8, pp. 442--443
• Sec. 28.11, pp. 448--449
• Sec. 30.1.1--30.2, pp. 460--464
• Sec. 30.3, pp. 466--467
• Sec. 31.1, pp. 469--470
• Sec. 31.1.2, pp. 475--476
• Sec. 31.1.4--31.1.4.5, pp. 477-479
• Sec. 33--35, pp. 482--488

Related: #640 (comment)

[Mo-Gul]

@hmenke, I would be happy to add the needed stuff, but currently I don't have a clue how (see also #640 (comment)). If you would provide one example how to add options to example environments in Lua I'll hopefully be able to do the rest.

[hmenke]

I'm closing this in favour of #640. We'll continue to track it over there.