Update formatting for genres in data.js file

[brittanyrw]

Let's make the genre array values more uniform. In the data.js file, format the genre arrays to the following:

• Genres should be all lowercase
• If genres are two words, they should be separated with a hyphen.

Incorrect genre formatting:

genres: ["Action", "True Crime",  "Adventure"]

Correct genre formatting:

genres: ["action", "true-crime",  "adventure"]

Update the README.md in the Card Overview section and the pull_request_template.md to make the directions more clear for how to format the genres.

[NitinNair89]

Happy to take this up. 👍