aLtErNaTiNg case converter

The convention starts lowercase, which matters more than it sounds: the format comes from the 2017 Mocking SpongeBob meme, where the alternation always begins on a lowercase letter, and a converter that starts uppercase produces something that reads subtly wrong to anyone who knows the format.

The alternation counts letters, not characters. Spaces and punctuation are passed through without advancing the alternation, so the pattern continues across a word boundary rather than resetting — aRe yOu rather than aRe yOu restarting at each word. That is what the original does and it is the detail that separates a correct implementation from an approximation.

Worth knowing if you are posting it: alternating case is genuinely hostile to screen readers. Some announce it letter by letter rather than as words, because the capitalisation pattern defeats the heuristics that decide whether a run of capitals is an acronym. The same applies to fancy Unicode text. It is fine in a reply where the joke is the point and worth avoiding anywhere the text carries information.