docfx

1. Fix html pre element behavior in Markdown, empty lines are now allowed in <pre> blocks.
2. Fix #1747: add app.config redirect binding to docfx to resolve LoaderException for docfx metadata
3. Fix #1737: it is now possible to use > [!warning] format in triple-slash comments
4. Fix #1319 that docfx fails to load multiple solutions
5. Fix #1720 and #1708 that docfx throws runtime error in Mono
6. Fix post processor incremental bug: restore manifest should be case-insensitive

PDF is now supported. Refer to Walkthrough: Generate PDF to get start with generating PDF files.

Fix default template performance bug that local search is always used.

1. Bug fix for markdown empty link.
2. Bug fix for html behaivor in dfm-latest.

Introduce Master page syntax into Template System:

1. Mustache: {{!master('<master_page_name>')}}
2. Liquid: {% master <master_page_name> %}

[Breaking Change] View model for ManagedReference.html.primary.tmpl is updated from {item: model} to model, if you overwrites ManagedReference.html.primary.tmpl in your own template, make sure to re-export the template file.

Simplify default template: now you only need to overwrite _master.tmpl to redesign the layout for the website.

Frontend improvement

1. Long namespace name in TOC will be word-wrapped now
2. Bug fix for docfx.js when navbarPath or tocPath is empty.