feat(plugins/rushjs) - Adds RushJS plugin

[Shockolate]

Standards checklist:

• The PR title is descriptive.
• The PR doesn't replicate another PR which is already open.
• I have read the contribution guide and followed all the instructions.
• The code follows the code style guide detailed in the wiki.
• The code is mine or it's from somewhere with an MIT-compatible license.
• The code is efficient, to the best of my ability, and does not waste computer resources.
• The code is stable and I have tested it myself, to the best of my abilities.

Changes:

• Adds a new plugin rushjs to ohmyzsh. The plugin consists of several aliases for developer convenience for those using the RushJS monorepo manager.

Other comments:

[z-hirschtritt]

+1