Bug Fix: The markdown rendering is mangled for backtick blocks.
Bug Fix: The markdown rendering is mangled for backtick blocks.

https://github.com/vector-im/vector-ios/issues/448

Note this commit pursues previous PR "Improve HTML rendering a bit" #137
- background-color is now working for <code> tag.

matrix-org/matrix-ios-kit,matrix-org/matrix-ios-kit,matrix-org/matrix-ios-kit,matrix-org/matrix-ios-kit