Closes https://github.com/zed-industries/zed/issues/41938 For some error messages relating to the keymap file, the font size was too large. This was due to the error message being a child `MarkdownString` instead of a `SharedString`. A `.text_xs()` method is being applied to this notification, but it appears not to affect the markdown text. I found that the H5 text size in markdown is the same size as other error messages, so I made each element (that had text) that size. There was also a special case for bullet points. I also added a gear icon to the settings button, so it was more in line with other app notifications. Error message (text too large):  Expected behavior (notification with correct text sizing and icon):  Example behavior:  Release Notes: - Improved UI for keymap error messages. --------- Co-authored-by: Danilo Leal <daniloleal09@gmail.com>