Used by subclasses to serialize extensions. Extension ranges may be
interleaved with field numbers, but we must write them in canonical
(sorted by field number) order. ExtensionWriter helps us write
individual ranges of extensions at once.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2024-10-10 UTC."],[],[]]