Enable automatic generation of a post glossary

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This feature would allow specific words to be tagged with a definition, and those definitions would automatically be parsed into a glossary section added to each page. The glossary entries would serve as anchors that are linked to by the first use of each word in the glossary on the page.

This would allow us to make clear the use of words and phrases in posts. For some concepts, it's important that we make our definitions explicit so that readers can compare with their assumptions of what we mean, and gain clarity if there are differences.