Fix 1st Line Indentation in Code Blocks

[tajmone]

Problem

After an Alan code block starting with an indentation is processed by Highlight, the indentation on the first line is lost.

• Fix all occurrences in current sources using the {wj} workaround.
• Before committing, check that it doesn't interfere with:
  • PDF builds (via Asciidoc-fopub).
  • Highlight.js (i.e. Alan Manual).

For more info on this problem, see: tajmone/hugo-book#15

For an example, see:

• The Hugo Book: 5.4. Init And Main (a106ed8).

The {wj} Workaround

Right now, the only workaround solution is to add a word joiner character (⁠) at the beginning of the first indented line using its predefined attribute for character replacement ({wj}):

[source,alan, subs="+attributes"]
---------------------------------
{wj}  Add To Every object

This works fine, although it's far from being an ideal solution (but, at least, it shouldn't create any problems for other Asciidoctor backends and output formats).