XiaoW_Add feature of auto restart server upon saving changes

[wang9hu]

Description

This PR adds a feature that auto restart the server upon any changes in the /src directory. By running npm run dev, developers do not need to rebuild and restart server, which improves development efficiency.

Main changes explained:

• add nodemon package for auto restarting upon changes
• add npm run dev command in package.json
• modify readme command description
• change parser from babel-eslint to @babel/eslint-parser in .eslintrc because babel-eslint is deprecated. For more info, check here
• remove babel-eslint package

How to test:

1. check into current branch
2. do npm install to install
3. do npm run dev to start the server
4. make changes to files in /src and save files, use frontend or other methods to verify that those changes can be reflected

Note:

Include the information the reviewers need to know.

[one-community]

Xiao W: "yeah, I believe it is ok to merge, it should be just a QoL improvement"