Prevent double ignore of .vercel folder

[selmansem]

Idea

What to fix?

When the project is linked using the CLI, it automatically adds the .vercel folder to the .gitignore file.
The thing is that there are times when the user already added the folder manually as .vercel/ with the / at the end.
The script that validates if it has already been added does not take it into consideration.

Idea

Validate if there are different variants.

Before: Link to code

if (!gitIgnore.split(EOL).includes(ignore)) {
    gitIgnore += `${
        gitIgnore.endsWith(EOL) || gitIgnore.length === 0 ? '' : EOL
    }${ignore}${EOL}`;
    contentModified = true;
}

After:

const regex = /\.vercel(?:$|\n|\/)/
if (!regex.test(gitIgnore)) {
    gitIgnore += `${
        gitIgnore.endsWith(EOL) || gitIgnore.length === 0 ? '' : EOL
    }${ignore}${EOL}`;
    contentModified = true;
}

Objective

Avoid redundancy and clean code.