Add doc/note for WUFFS_BASE__QUIRK_IGNORE_CHECKSUM
diff --git a/doc/note/quirks.md b/doc/note/quirks.md
index fdeb021..b1c1302 100644
--- a/doc/note/quirks.md
+++ b/doc/note/quirks.md
@@ -48,5 +48,16 @@
## Listing
+Common quirks:
+
+- `WUFFS_BASE__QUIRK_IGNORE_CHECKSUM` configures decoders (but not encoders) to
+ skip checksum verification. This can result in [noticably faster
+ decodes](https://github.com/google/wuffs/commit/170a8104867fa818d329d85921012c922577c955),
+ at a cost of being less able to detect data corruption and to deviate from a
+ strict reading of the relevant file format specifications, accepting some
+ inputs that are technically invalid (but otherwise decode fine).
+
+Package-specific quirks:
+
- [GIF image decoder quirks](/std/gif/decode_quirks.wuffs)
- [JSON decoder quirks](/std/json/decode_quirks.wuffs)
