activate highlight.js

- It supports everything we need except HAL syntax (of course not),
- it supports autodetection of code type,
- the notation "{ini}" leads to autodetection - but probably using "ini" is fine with asciidoctor
- highlight.js is currently accessed online --> has to be included in the repository for offline docs

docs/src/config/ini-config.adoc

@@ -1,5 +1,6 @@
 :lang: en
 :toc:
+:source-highlighter: highlight.js
 
 [[cha:ini-configuration]]
 = INI Configuration(((INI Configuration)))
@@ -106,7 +107,7 @@ whitespace following the trailing backslash character.
 Section identifiers may not be extended to multiple lines.
 
 .Variable with Line extends Example
-[source,{ini}]
+[source,ini]
 ----
 APP = sim_pin \
 ini.0.max_acceleration \
@@ -134,7 +135,7 @@ To add a custom variable to an existing LinuxCNC section, simply include
 the variable in that section.
 
 .Custom Variable Example
-[source,{ini}]
+[source,ini]
 ----
 [JOINT_0]
 TYPE = LINEAR
@@ -482,7 +483,7 @@ path to the program or be located in a directory that is on the system path.
 
 It is also possible to specify an interpreter:
 
-[source,{ini}]
+[source,ini]
 ----
 PROGRAM_EXTENSION = .py Python Script
   py = python

docs/src/gcode/g-code.adoc

@@ -1,5 +1,6 @@
 :lang: en
 :toc:
+:source-highlighter: highlight.js
 
 [[cha:g-codes]]
 = G-Codes
@@ -1094,8 +1095,9 @@ an encoder (or resolver) counter which resets index-enable once per rev.
 See the Integrators Manual for more information on spindle synchronized
 motion.
 
+// this seems to enable auto detection of source type
 .G33 Example
-[source,{ngc}]
+[source,'']
 ----
 G90 (absolute distance mode)
 G0 X1 Z0.1 (rapid to position)
@@ -1119,7 +1121,8 @@ It is an error if:
 [[gcode:g33.1]]
 == G33.1 Rigid Tapping(((G33.1 Rigid Tapping)))
 
-[source,{ngc}]
+// this should force gcode style, but doesn't actually
+[source,gcode]
 ----
 G33.1 X- Y- Z- K- I- $-
 ----