fix(mocha): force color output for mocha logs

As with many CLI tools, mocha supports ANSI colours for its test
reporting but disables them if it's not connected to a TTY (i.e., if
it's not an interactive session, such as when it's run in a CI or if
it's being piped to another script). It doesn't detect a TTY in our case
as we're piping its stdout and stderr through our winston logging
infrastructure rather than outputting to the user's terminal directly.
In order to get colourful output then, let's force it via mocha's
--color option.

plugins/mocha/src/tasks/mocha.ts

@@ -12,7 +12,7 @@ export default class Mocha extends Task<typeof MochaSchema> {
   async run(): Promise<void> {
     const files = await promisify(glob)(this.options.files)
 
-    const args = [this.options.configPath ? `--config=${this.options.configPath}` : '', ...files]
+    const args = ['--color', this.options.configPath ? `--config=${this.options.configPath}` : '', ...files]
     this.logger.info(`running mocha ${args.join(' ')}`)
     const child = fork(mochaCLIPath, args, { silent: true })
     hookFork(this.logger, 'mocha', child)