[v0.9.1] Add docs/source/confg.py print (#1187)

### What this PR does / why we need it?
Add myst_substitutions print in docs/source/confg.py

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
CI passed

Signed-off-by: Yikun Jiang <yikunkero@gmail.com>

Author: Yikun

docs/source/conf.py

@@ -23,6 +23,7 @@
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #
+import json
 import os
 
 # import sys
@@ -133,3 +134,7 @@
 
 def setup(app):
     pass
+
+
+if __name__ == "__main__":
+    print(json.dumps(myst_substitutions))