Render math in Asciidoc and Markdown with KaTeX using code blocks

app/assets/javascripts/blob_edit/edit_blob.js

app/assets/javascripts/notes.js

app/assets/javascripts/preview_markdown.js

app/assets/javascripts/render_gfm.js

app/assets/javascripts/render_math.js

app/assets/javascripts/syntax_highlight.js

changelogs/unreleased/8003-katex-math.yml

config/application.rb

config/initializers/math_lexer.rb

doc/user/markdown.md

lib/banzai/filter/inline_math_filter.rb

lib/banzai/filter/math_filter.rb

lib/banzai/filter/syntax_highlight_filter.rb

lib/banzai/pipeline/gfm_pipeline.rb

lib/gitlab/asciidoc.rb

lib/gitlab/gon_helper.rb

lib/rouge/lexers/math.rb

spec/lib/banzai/filter/inline_math_filter_spec.rb

spec/lib/banzai/filter/math_filter_spec.rb

spec/lib/gitlab/asciidoc_spec.rb