Added requirements.txt for doc build

requirements-doc.txt

@@ -0,0 +1,12 @@
+mkdocs
+mkdocs-macros-plugin
+mkdocs-exclude
+markdown-include
+mkdocs-material
+mkdocs-with-pdf
+mkdocs-git-revision-date-plugin
+mkdocs-material-extensions
+mkdocs-bootstrap-tables-plugin
+mkdocs-section-index
+mkdocs-htmlproofer-plugin
+mike