'Local Development' part of the README file needs to be modified.

[DigitalBard]

Describe the bug
When I followed the steps of the "Local Development" part of README file, I got an error like below:

That's because when I did yarn build-dev, the dist directory was incomplete.

And there was another warning like this:

But when I followed the 'Getting set up' part of 'CONTRIBUTING.md' file, everything was okay.

To Reproduce
Steps to reproduce the behavior:

1. Clone the project by "git clone".
2. yarn install
3. yarn build-dev
4. yarn start

Expected behavior
So, I recommend to modify the 'Local Development' part of the 'README file' like 'Getting set up' part of 'CONTRIBUTING.md' file,
or rewrite simply like "Please refer to 'CONTRIBUTING.md' file."

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Chrome

[yuki0410-dev]

@DigitalBard (cc. @martijnrusschen )
It looks like the PRs have already been merged, are there any other issues?