Don't let clang-format reorder Fiddle `#include`s (#7887)

The documentation added by #6844 included instructions to make sure that
the Fiddle `#include` in a file comes after all the other `#include`s,
but it's easy to accidentally violate this via `clang-format`, as
happened for `source/slang/slang-ast-modifier.h` in #7559. This PR
guards against this sort of violation by separating all Fiddle
`#include`s from other `#include`s via a blank line followed by a `//`
line (as we already do in most cases), and also adds a sentence about
this in `tools/slang-fiddle/README.md`.

As a bonus, I also enabled Markdown syntax highlighting for all the code
blocks in that doc file.

Co-authored-by: Ellie Hermaszewska <ellieh@nvidia.com>

4 files changed, 9 insertions, 1 deletions

diff --git a/source/slang/slang-ast-expr.h b/source/slang/slang-ast-expr.h
index 32c724e10..adbc7a2ba 100644
--- a/source/slang/slang-ast-expr.h
+++ b/source/slang/slang-ast-expr.h
@@ -2,6 +2,8 @@
 #pragma once
 
 #include "slang-ast-base.h"
+
+//
 #include "slang-ast-expr.h.fiddle"
 
 FIDDLE()
diff --git a/source/slang/slang-ast-modifier.h b/source/slang/slang-ast-modifier.h
index b5fa25418..2f9c29d6c 100644
--- a/source/slang/slang-ast-modifier.h
+++ b/source/slang/slang-ast-modifier.h
@@ -2,9 +2,11 @@
 #pragma once
 
 #include "slang-ast-base.h"
-#include "slang-ast-modifier.h.fiddle"
 #include "slang-ir-insts-enum.h"
 
+//
+#include "slang-ast-modifier.h.fiddle"
+
 FIDDLE()
 namespace Slang
 {
diff --git a/source/slang/slang-ast-stmt.h b/source/slang/slang-ast-stmt.h
index f5436a70e..485ddd439 100644
--- a/source/slang/slang-ast-stmt.h
+++ b/source/slang/slang-ast-stmt.h
@@ -2,6 +2,8 @@
 #pragma once
 
 #include "slang-ast-base.h"
+
+//
 #include "slang-ast-stmt.h.fiddle"
 
 FIDDLE()
diff --git a/source/slang/slang-ast-val.h b/source/slang/slang-ast-val.h
index f371d76fe..a381410b6 100644
--- a/source/slang/slang-ast-val.h
+++ b/source/slang/slang-ast-val.h
@@ -3,6 +3,8 @@
 
 #include "slang-ast-base.h"
 #include "slang-ast-decl.h"
+
+//
 #include "slang-ast-val.h.fiddle"
 
 FIDDLE()