[Bug] - Default language "JavaScript" should be uppercase

### What bug did you find in the codebase?

The `defaultLanguage` constant `lang` prop should be uppercase.

Current code:
`
const defaultLanguage: LanguageType = {
  lang: "JavaScript",
  icon: "/icons/javascript.svg",
};
`

On initial load the selector reads "JavaScript" but after changing to another language and then back it reads "JAVASCRIPT", which is what it should read initially.