Use chat variables instead of slash commands

[shouples]

The parts of the original blog post are only accessed directly when invoked from the existing slash commands, but we should be able to use them in other ways.

The variables API is still in a proposed state (microsoft/vscode#212995), but eventually they should be used here.

vscode-grug-chat/src/chat/participant.ts

Lines 87 to 89 in 7f262f8

	} else if (BLOG_THOUGHT_SECTIONS.includes(`${command}.md`)) {
	stream.progress(`grug think about ${command}...`);
	thoughtReference = await getGrugReferenceContent(`${command}.md`);