Closes #2753

Closes #2855

Issue #2870

To be more intelligent about what kind of lines to indent.

- Using `@` as `this`
- `and=` and `&&=`
- `or=` and `||=`
- `?=`

Closes issue #2832

Closes #2851

Fixed indentation for covergroups
Fixed indentation for import/export statements
Better handling of 'function' keyword in other contexts

Closes #2817

Also update the mode loading demo to make use of the info in that
file, allowing filenames and mimes to be entered.

Issue #2828

Added file extensions to the meta info. Added helper functions
getExtFromMimeType,  getMimeTypeFromExt, getFilenameAndExt from a file
name, and detectCodeMirrorMode from a mime type

Issue #2807
Issue #2814

Closes #2816

Closes #2813

after header immediately followed by a code block, GFM formatting is
broken (SHA, #issue, URLs).

overlay.codeBlock gets it wrong (false inside fenced block, true after).
Not yet sure why.

Throwing exceptions is a really bad way to deal with unexpected
syntax in a highlighting mode.

Closes #2805

Closes #2810

Closes #2796

Closes #2794

Issue #2792

Issue #2786