HUD messages

Subject to change in following versions.

Example implementation: https://github.com/Deraen/less4clj/blob/master/boot-less/src/deraen/boot_less.clj#L104-L111

Shared data format for exception data or warning.

{:message "Message"
 :file "src/css/main.less.less"
 :line 10
 :column 1}

Exceptions

• Legacy ex-data contains :from property with value :boot-cljs
• ex-data contains property :adzerk.boot-reload/exception with truthy value

Warnings

• Legacy :adzerk.boot-cljs/warnings from .cljs.edn file fileset metadata
• :adzerk.boot-reload/warnings from fileset metadata of any file

TODO

• Support error/warning context, should probably contain few lines of code near the error, and information to display proper line numbers for those lines (e.g. start line)
• Should support showing multiple errors, e.g. boot-less can return multiple errors