Adds an arrow that can be used to collapse markdown headers

• All markdown headers become clickable and will toggle the view of all content between same level headers (e.g. between H2 headers).
• It works on readme, issues, markdown preview, wiki & gist pages. Pretty much everywhere on GitHub.
• Click on any header to toggle the view of the content below it.
• Use Shift + Click to toggle the view of all same level header content.
• When the content of a header is expanded, all sub-headers are also expanded.
• Links within the header are still clickable.
• Each header level arrow can get a color set making it easier to distinguish header levels.
• This portion of the Chrome extension was originally written as a userscript.

• "Enabled" - Check to enable the markdown collapse script.
• "Animated" - Check to enable animation of content; added in v1.1.0.
• "Initial State" - Set to "Collapsed" (default) to have all header content initially collapsed, or "Expanded" to leave the markdown as-is.
• "Arrow Colors" - Click on any of the color swatches to change the arrow color associated with each header (H1 through H6). The default palette was generated from iwanthue using colorblind friendly, soft colors.