DOC: Point to dev-docs in issue template (#17353)

[ci skip]

Author: gfyoung

.github/ISSUE_TEMPLATE.md

@@ -12,6 +12,12 @@
 
 **Note**: Many problems can be resolved by simply upgrading `pandas` to the latest version. Before submitting, please check if that solution works for you. If possible, you may want to check if `master` addresses this issue, but that is not necessary.
 
+For documentation-related issues, you can check the latest versions of the docs on `master` here:
+
+https://pandas-docs.github.io/pandas-docs-travis/
+
+If the issue has not been resolved there, go ahead and file it in the issue tracker.
+
 #### Expected Output
 
 #### Output of ``pd.show_versions()``