This is the syntax definition for Old-Style ASCII Property Lists. That is an outdated property list format like Xcode still uses it in its project files. Sometimes one has to jump in those and edit them in the text format they are. This syntax definition improves readability by enabling coloring.
This is not yet available on Package Control at the time of writing.
Otherwise it can be installed manually by cloning the repository in your package directory of Sublime Text.
Please see CONTRIBUTING.md.
Please see LICENSE.md.