Detect and ignore base64 encoded data

[Skylion007]

When trying to run typos on iPython notebooks like Google Colabs, it destroys all the base64 data inside of the notebook [banana.jpg]. Base64 is not necessarily a spelling error: For example running it in this folder mangles the notebooks: https://github.com/facebookresearch/habitat-sim/tree/master/examples/tutorials/colabs .

[epage]

Short term, I'd recommend

[type.jupyter]
check-file = false

See https://github.com/crate-ci/typos#false-positives

Longer term, we are discussing in #270 for ignoring hashes, and base64. Since that issue is titled for hashes, I'll leave this one open to track also addressing base64. Keeping them focused can help in if we don't address them at the same time.