Typo and incorrect wording in contribute.md

Hello,

Sorry to disturb for such a small issue. I came across your project today and while exploring the [website](http://gitjournal.io), I discovered a typo that bothered me :sweat_smile:

On the contribute page it's written: `GitJournal is an [Open Souce project](https://github.com/GitJournal/GitJournal), and can always use the help.` instead of Open Sou**r**ce.

Moreover the term ´Open Source´ should only apply for the Open Source Initiative.
As an adjective it should be hyphenated like : `open-source` (see [recommendation](https://learn.microsoft.com/en-us/style-guide/a-z-word-list-term-collections/o/open-source)).

If you think it's relevant I made a quick patch or I can submit a PR if you prefer.

[fix_typo_+_correct_term.patch](https://github.com/GitJournal/gitjournal.io/files/14787918/fix_typo_%2B_correct_term.patch)

Regards,

Fabien