feat(gogs): setup

[shreyas1599]

#117

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• TODO: for now fetchGogs uses the template of bitbucket. Will refactor when I refactor that
• Lot of attributes were missing in the API response. API seems to be in very early stages. I added comments to indicate this wherever appropriate
• In some places I used this name: p.fullName.split('/')[1]. I'm not sure whether I should perform the processing while building the widget or create a getter in gogs.dart and move this there?
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