Fix Gatsby config filename

[eli8levit]

In #188 PR there was added an icon to the Gatsby config file. But according to the Gatsby docs the filename should be gatsby-config.js instead of gatsby.config.js.

In addition, I've added gatsby-node.js filename to the same icon according to this Gatsby guide.

[PKief]

Thank you! Could you please insert all file names into one array and leave the old gatsby.config.js in it:

{ name: 'gatsby', fileNames: ['gatsby.config.js', 'gatsby-config.js', 'gatsby-node.js'] }

[eli8levit]

Sure!

[PKief]

Thank you 👍

[eli8levit]

@PKief Thank you! I'm using your theme for a long time and it's awesome 👏

[PKief]

@JediYozh I'm glad you like it, thank you! 😃