Create README.md

Initial readme with some background information

README.md

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+# AirlineSim Enhancement Suite
+
+The AirlineSime Enhancement Suite (AES) offers a set of tools to help CEOs build their airlines.
+
+## Features
+
+- Aircraft profitability calculator
+- A route analyser which shows load factors for routes
+- A salary adjuster that uses the country average as a base
+- Competitor monitoring software
+
+## Installation
+
+Supported platforms: chromium based browsers (Chrome, Edge, etc)
+
+Please follow [racsofp’s guide](https://forums.airlinesim.aero/t/manual-installation-of-the-ase-airlinesim-enhancement-suite-chrome-extension/24671)
+
+## History
+
+Marcipanas is the original developer of this plugin.
+It seems they ceased development sometime in 2020.
+The community has published some updates in the meantime but no continued development has happened since.
+
+## Credits
+
+- Marcipanas for the original development
+- racsofp for their update and installation documentation