Provide summary of errors when in --pretty mode? #22124
Description
TypeScript Version: 2.7.1
Search Terms: error watch summary pretty mode file counts
When refactoring large projects, the CLI output from compile runs (both from solo compiles and --watch) can build up pretty quickly. Every time I save a file it feels like the terminal is filling up with a giant sea of angry errors.
It would be convenient to have an error around the lines of "Found 43 errors in 21 files." at the bottom of each compile to help track progress.
IMO this should be on only for --pretty mode since that's intended for human consumption.