TL schema describes types and functions for rpc protocol and binary serialization format. You can read about it here. TL is used primarily by VK and Telegram.
This plugin brings lexer/parser, highlighting, go to and other stuff for .tl files.
Just install the plugin to any IDE from Marketplace in Settings > Plugins.
Note! This plugin was initially developed in 2016, it doesn't use Gradle, it's just plain Java project.
How to complile .jar. Open project in IDEA and choose Platform Plugin SDK as Project SDK. Make sure that Grammar Kit plugin is installed. Generate parser from .bnf file (using context menu), then execute JFlex on .flex file (also with context menu). Include src/ and gen/ folders as sources of module. Define an artifact from compiler output adding META-INF folder. Finally, produced .jar is supposed to be installed to development IDE instance.