Update some configuration for development experience

[Keith-CY]

1. add a format npm script and run it with staging files on committing;
2. update prettier to remove semicolons.

[Keith-CY]

PR: #44

[homura]

Using semi will make the code style consistent, so it is recommended to use semi

Certain ECMAScript statements (empty statement, variable statement, expression statement, do-while statement, continue statement, break statement, return statement, and throw statement) must be terminated with semicolons

https://262.ecma-international.org/5.1/#sec-7.9

[Keith-CY]

Using semi will make the code style consistent, so it is recommended to use semi

Certain ECMAScript statements (empty statement, variable statement, expression statement, do-while statement, continue statement, break statement, return statement, and throw statement) must be terminated with semicolons

262.ecma-international.org/5.1/#sec-7.9

This is just a matter of code style and has been agreed upon by other members.

The title of the section referenced above is Automatic Section Insertion which is known as ASI that specifies how the semicolon should be inserted by interpreter. The conclusion of this section These situations are described by saying that semicolons are automatically inserted into the source code token stream in those situations. also proves it.

And the specification/TC39 committee has no bias on the code style

Ref: tc39/ecma262#1062 (review)