TRACKING: Message rendering bugs/enhancements

[neiljp]

• Empty link bug Improve handling of empty-label links #1103
• Render heading titles Emphasize heading titles in messages #1095
• Render horizontal rulers
• New markdown feature: Mention a time #691 : Mentioning times (with automatic time zone adjustment) [PR Markup timezone-aware time mentions #765]
• Add support for spoilers #688 : Spoilers
• Fix quoted text rendering (mixing '>' and ```quote ?) #402 : quoting (other cases may be present)
• List links at end of message (and/or in popup?) #618 : List links at end of message (and/or in popup?) [also see Opens message links popup menu #424 PR] (fixed in MessageBox: Extract in-line message links from the message content and show them as footlinks #703/Handle internal links #708)
• Render tables (boxes/helper: Add support for rendering tables. #550)
• Cross reference internal links to their respective narrows within ZT #352 : Interpret internal links to messages in other streams/topics, and handle them [PR Handle internal links #708]
• WIP: Support displaying of images in msg in the default viewer. #359 PR: Images in the default browser [also PR [WIP] Handle media links #740, Add media support in ZT #1058, Media opening (slight reorder & tidy of #1058) #1223]
• keys: Add a key to view a message in the browser. #397 PR: Viewing a message in the browser [also PR [WIP] Add support for viewing a message in the web browser #698]
• ASCII/Unicode in-application approximate rendering of images #415 Ascii images

[preetmishra]

Update: 4: List links at end of message (and/or in popup?) has been resolved in #703 and #708.

[zee-bit]

Update: The last point (Add a key to view a message in the browser) has been resolved through #991.