Implement enableMarkdown settings to allow users to disable markdown …

[alex-bellomo]

Issue #, if available:

• None.

Why make this change:

• This was personally bothering me as a user - asking Q to generate markdown-formatted text (e.g. CR descriptions) would result in rendered markdown. I would have to re-format the output after pasting it into CRUX.

Description of changes:

• Created a new chat setting, enableMarkdown, that users can use to disable markdown rendering in the responses. The setting defaults to true, unless specified false by the user.
• When the enableMarkdown setting is set to false, skip the markdown-related parsers in parse.rs.
• Added unit tests to validate behavior.

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