Add syntax coloring for code blocks in the README

[mh-cbon]

No description provided.

[coveralls]

Coverage remained the same at 67.081% when pulling 088c6c0 on mh-cbon:patch-1 into 2b39596 on kelvins:master.

[kelvins]

Hello @mh-cbon, thanks a lot for your contribution to the project.

Can you please just fix the indentation?

For example:

    CREATE DATABASE rest_api_example;
    USE rest_api_example;
    CREATE TABLE users (
        id INT AUTO_INCREMENT PRIMARY KEY,
        name VARCHAR(50) NOT NULL,
        age INT NOT NULL
    );

to

CREATE DATABASE rest_api_example;
USE rest_api_example;
CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    age INT NOT NULL
);