add RST highlighting for command line / shells (also fixes #16858) (#17789)

doc/docstyle.rst

@@ -6,17 +6,17 @@ General Guidelines
 
 * See also `nep1<https://nim-lang.github.io/Nim/nep1.html>`_ which should probably be merged here.
 * Authors should document anything that is exported; documentation for private
-  procs can be useful too (visible via `nim doc --docInternal foo.nim`).
+  procs can be useful too (visible via `nim doc --docInternal foo.nim`:cmd:).
 * Within documentation, a period (`.`) should follow each sentence (or sentence fragment) in a comment block.
   The documentation may be limited to one sentence fragment, but if multiple sentences are within the documentation,
   each sentence after the first should be complete and in present tense.
 * Documentation is parsed as a custom ReStructuredText (RST) with partial markdown support.
 * In nim sources, prefer single backticks to double backticks since it's simpler
-  and `nim doc` supports it. Likewise with rst files: `nim rst2html` will render those as monospace, and
-  adding `.. default-role:: code` to an rst file will also make those render as monospace when rendered directly
+  and `nim doc`:cmd: supports it. Likewise with ``rst`` files: `nim rst2html`:cmd: will render those as monospace, and
+  adding ``.. default-role:: code`` to an ``rst`` file will also make those render as monospace when rendered directly
   in tools such as github.
-* In nim sources, for links, prefer `[link text](link.html)` to `` `link text<link.html>`_ ``
-  since the syntax is simpler and markdown is more common (likewise, `nim rst2html` also supports it in rst files).
+* (debatable) In nim sources, for links, prefer ``[link text](link.html)`` to `\`link text<link.html>\`_`:code:
+  since the syntax is simpler and markdown is more common (likewise, `nim rst2html`:cmd: also supports it in ``rst`` files).
 
 .. code-block:: nim
 
@@ -29,7 +29,7 @@ Module-level documentation
 --------------------------
 
 Documentation of a module is placed at the top of the module itself. Each line of documentation begins with double hashes (`##`).
-Sometimes `##[ multiline docs containing code ]##` is preferable, see `lib/pure/times.nim`.
+Sometimes `##[ multiline docs containing code ]##` is preferable, see ``lib/pure/times.nim``.
 Code samples are encouraged, and should follow the general RST syntax:
 
 .. code-block:: Nim
@@ -76,11 +76,11 @@ Whenever an example of usage would be helpful to the user, you should include on
     ##  echo execCmdEx("git pull")
     ##  drawOnScreen()
     runnableExamples:
-      # `runnableExamples` is usually preferred to `code-block`, when possible.
+      # `runnableExamples` is usually preferred to ``code-block``, when possible.
       doAssert addThree(3, 125, 6) == -122
     result = x +% y +% z
 
-The command `nim doc` will then correctly syntax highlight the Nim code within the documentation.
+The command `nim doc`:cmd: will then correctly syntax highlight the Nim code within the documentation.
 
 Types
 -----