Add smile to rstcheck ignore

Author: ericholscher

docs/.rstcheck.cfg

@@ -1,7 +1,7 @@
 [rstcheck]
 ignore_directives=automodule,http:get,tabs,tab,prompt,http:patch,http:post,http:put,http:delete
 ignore_roles=djangosetting,setting,featureflags,buildpyversions
-ignore_substitutions=org_brand,com_brand
+ignore_substitutions=org_brand,com_brand,:smile:
 # This error needs to be ignored for now
 # See: https://github.com/myint/rstcheck/issues/19
 ignore_messages=(Hyperlink target ".*" is not referenced)