Yarn run docs:dev stops execution after changing config.js

[alex-w0]

• I confirm that this is an issue rather than a question.

Bug report

Hi, when I'm starting vuepress on a local webserver and editing the config.js the execution of the yarn script will be stopped.

Steps to reproduce

1. Clone the minimalistic project from my repository and install the dependencies
   https://github.com/alex-w0/test_vuepress

2. Run the webserver which will be accessible on localhost:8080
   yarn run docs:dev

3. Go the the vuepress/config.js and change the title to something else. Afterwards the yarn task will be rerendered but it stopped during the process.
   

It basically happens when I'm changing the yaml content. I've to rerun the task to apply the yaml changes.

[meteorlxy]

Related to #1283 (may be duplicated)