Add RPG syntax highlighter package

[tegansnyder]

• I'm the package's author and/or maintainer.
• I have read [the docs][1].
• I have tagged a release with a [semver][2] version number.
• My package repo has a description and a README describing what it's for and how to use it.
• My package doesn't add context menu entries. *
• My package doesn't add key bindings. **
• Any commands are available via the command palette.
• Preferences and keybindings (if any) are listed in the menu and the command palette, and open in split view.
• If my package is a syntax it doesn't also add a color scheme. ***
• I use [.gitattributes][3] to exclude files from the package: images, test files, sublime-project/workspace.

My package is an RPG/ILE RPG syntax highlighting package for Sublime Text 3, covering both free-format and fixed-format RPG, plus embedded SQL highlighting and RPG-specific completions/snippets.

My package is similar to the original RPG package by Niels Liisberg. However it should still be added because this package is updated for Sublime Text 3 with a native .sublime-syntax grammar, improved RPG token coverage, fixed-format and free-format support refinements, embedded SQL handling, and active maintenance.

[braver]

Have you tried contributing to the original package?