Use Database API in GitHubManager to handle larger files

[yyykt]

Problem

Currently, GitHubManager uses Contents API to obtain file diffs from GitHub. Since this API only supports files up to 1 MB, the following error was displayed when I tried to review a notebook with some image outputs.

Load File Error (Invalid response: 403 This API returns blobs up to 1 MB in size. The requested blob is too large to fetch via the API, but you can use the Git Data API to request blobs up to 100 MB in size.)

Proposed Solution

I think this situation can be solved by using Database API instead, which supports blobs up to 100 MB.

Additional context

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[bollwyvl]

Sure, this sounds good to investigate. Note, of course, that a lot of visual features start to break down with assets of large size when viewed in the browser, so anything that starts to get close to that 100mb is not going to feel very responsive...