Improve Readme

Start with the README and compare its instructions with package.json, manifest.ini, setup.py, and src/demo/App.js. Check the React guidance and dash-core-components reference mentioned in the issue, then verify the npm and PyPI publishing steps. Done means the README clearly explains replacements, dependencies, demo commands, packaging, login, and publishing prerequisites.

Hi everyone,

I made a few suggestions on the Readme. For a beginner like me, I had a lot of questions when I tried to create my own component. I have listed them below. My apologies if some suggestions are dumb/super-obvious: I had a difficult time figuring them out.

Pointer 2.
Find-and-replace:
my_dash_component with your component library name.
I think it should be made clear about replacing it everywhere: for eg: in package.json, manifest.ini. setup.py etc.

Pointer 3:
Note: Relevant dependencies must be isntalled for the component you are creating.

Pointer 4:
It wasnt very clear when I read ' it opens the JS Demo environment' - like does npm start would open a demo-environment. I then realized that it would be running the App.js in the demo folder under src. Ask the users to go through the package.json to see what the npm commands are setup to do.

Pointer 5:
Please link the

React Document - React for python devs

to help create the component. Also please mention how the version of React is critical. I realized that there are big changes to how code is written in React 15 and 16. Also refer to the react code for dash-core-components, so that users can see how the react component is written.

Pointer 7 iii:
Add Note: If the MANIFEST.INI does not have the correct references, the tarball would still be created without error but wouldn't work in the local environment. For eg. In my case, the error said that package.json was not found in my_dash_component, but when I looked into the my_dash_component in the repo, it was there. This means, the files did not get correctly copied to the tarball.

Pointer 7 iv:
npm run publish did not work for me. I had to use npm publish.

BEFORE publishing the component, the user needs to first login using npm adduser. If not, npm throws a misleading error "Please try running this command again as root/Administrator." Please refer to this for more details on this issue: https://github.com/npm/npm/issues/20450.

Do a similar thing for PyPi: login before publishing.