fix: make typescriptformatter support 0.5 of fork checker

Created by: SimenB

I use the formatter in an ejected project, and got errors after updating to the latest version of fork-ts-checker-webpack-plugin. The changes in this PR should make it compatible with both 0.4.x and 0.5.0.

See https://github.com/Realytics/fork-ts-checker-webpack-plugin/pull/182

I've tested by building my project using the formatter with both 0.4.15 and 0.5.0