* build: add google's diff-match-patch
Copied from 62f2e689f4/java/src/name/fraser/neil/plaintext/diff_match_patch.java
* feat(status/edit-history): display diff for text
Closes https://github.com/sk22/megalodon/issues/789
* fix(status/edit-history): add fake poll id
* code style adjustments
* don't diff if only formatting changed
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Co-authored-by: sk <sk22@mailbox.org>