Improve issue templates for bug reporting.

.github/ISSUE_TEMPLATE/bug_report.md

@@ -14,6 +14,13 @@ A clear and concise description of what the bug is.
 Steps to reproduce the behavior:
 ```
 <Paste your command-line here which cause the problem>
+
+$ git clone htps://github.com/.../some_project
+$ cd some_project
+$ pip install -r requirements.txt
+$ cd docs
+$ make html SPHINXOPTS="-D language=de"
+$ # open _build/html/index and see bla bla
 ```
 
 **Expected behavior**
@@ -29,6 +36,7 @@ If applicable, add screenshots to help explain your problem.
 - OS: [e.g. Unix/Linux/Mac/Win/other with version]
 - Python version: [e.g. 3.7.1]
 - Sphinx version: [e.g. 1.8.2]
+- Sphinx extensions:  [e.g. sphinx.ext.autodoc, recommonmark]
 - Extra tools: [e.g. Browser, tex or something else]
 
 **Additional context**