markdown: Add rendered_content selector to night-mode syntax highlight.
markdown: Add rendered_content selector to night-mode syntax highlight.

This adds a parent selector, `rendered_content`, to night mode syntax
lighlight selector. This helps us in getting the "day mode" syntax
highlight styles in night mode.

timabbott/zulip,shubhamdhama/zulip,timabbott/zulip,showell/zulip,shubhamdhama/zulip,brainwane/zulip,kou/zulip,kou/zulip,shubhamdhama/zulip,rht/zulip,punchagan/zulip,tommyip/zulip,kou/zulip,shubhamdhama/zulip,punchagan/zulip,timabbott/zulip,eeshangarg/zulip,brainwane/zulip,brainwane/zulip,zulip/zulip,hackerkid/zulip,rht/zulip,brainwane/zulip,shubhamdhama/zulip,eeshangarg/zulip,punchagan/zulip,zulip/zulip,kou/zulip,synicalsyntax/zulip,showell/zulip,brainwane/zulip,andersk/zulip,rishig/zulip,punchagan/zulip,rht/zulip,zulip/zulip,hackerkid/zulip,tommyip/zulip,zulip/zulip,kou/zulip,hackerkid/zulip,eeshangarg/zulip,showell/zulip,kou/zulip,andersk/zulip,rht/zulip,rht/zulip,rishig/zulip,rishig/zulip,eeshangarg/zulip,tommyip/zulip,rishig/zulip,synicalsyntax/zulip,rht/zulip,andersk/zulip,brainwane/zulip,hackerkid/zulip,eeshangarg/zulip,hackerkid/zulip,timabbott/zulip,zulip/zulip,andersk/zulip,eeshangarg/zulip,timabbott/zulip,timabbott/zulip,synicalsyntax/zulip,andersk/zulip,tommyip/zulip,shubhamdhama/zulip,rishig/zulip,synicalsyntax/zulip,timabbott/zulip,synicalsyntax/zulip,rishig/zulip,punchagan/zulip,punchagan/zulip,rht/zulip,synicalsyntax/zulip,andersk/zulip,rishig/zulip,tommyip/zulip,showell/zulip,zulip/zulip,synicalsyntax/zulip,hackerkid/zulip,brainwane/zulip,shubhamdhama/zulip,andersk/zulip,hackerkid/zulip,showell/zulip,kou/zulip,punchagan/zulip,tommyip/zulip,showell/zulip,eeshangarg/zulip,tommyip/zulip,zulip/zulip,showell/zulip