Update docs to include markdown
What does this MR do and why?
After gitlab-vscode-extension!1554 (merged), gitlab-org/editor-extensions/gitlab-jetbrains-plugin!414 (merged), and gitlab-org/editor-extensions/gitlab.vim!125 (merged) merges, then Markdown will be supported by Code Suggestions inside VS Code, Neovim, and JetBrains.
This MR updates the docs table of supported languages to reflect this.
For #443365 (closed)
MR acceptance checklist
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Edited by Missy Davies