doc: try to fix code highlighting on docs site

mkdocs.yml

@@ -27,6 +27,7 @@ theme:
  accent: green
  features:
  - content.code.copy
+ - content.code.select
  - navigation.instant
  - navigation.instant.progress
  - navigation.tabs
@@ -43,8 +44,8 @@ markdown_extensions:
  - footnotes # enables inline footnotes by using [^1] to mark and [^1]: to define
  - pymdownx.mark # enables markdown highlighting with `==text==` syntax
  - pymdownx.tilde # enables markdown strikethrough with `~~text~~` syntax
- - pymdownx.snippets # grabs snippets from files instead of copy/pasting (https://facelessuser.github.io/pymdown-extensions/extensions/snippets/)
- - pymdownx.inlinehilite
+ - pymdownx.superfences # prerequisite for code highlighting
+ - pymdownx.inlinehilite # in line code syntax highlights
  - pymdownx.highlight:
  anchor_linenums: true
  use_pygments: true