Document LogViewer in features and usage pages

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LogViewer, steps on how to use it and the different functionality it provides should be documented so that it can be linked when prompting users in the community to provide logs about the OS or a specific app.

There can be a brief description in the features page, leading to a more complete breakdown in the usage guide.

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Additionally, a portion of https://grapheneos.org/usage#bugs-uncovered-by-security-features should be replaced to recommend LogViewer over a traditional bug report via developer options:

If you run into an application aborting, try to come up with a process for reproducing the issue and then capture a bug report via the 'Take bug report' feature in Developer options. Report an issue to the GrapheneOS OS issue tracker and email the bug report capture zip to [email protected] with the issue tracker number in the subject like "Bug report capture for issue #104". The bug report capture includes plain text 'tombstones' with logs, tracebacks, address space layout, register content and a tiny bit of context from memory from areas that are interesting for debugging. This may contain some sensitive data. Feel free to provide only the tombstone for the relevant crash and filter out information you don't want to send. However, it will be more difficult to debug if you provide less of the information. If the app doesn't work with sensitive information, just send the whole tombstone.