Clarify setting license via environment variable

[gdereese]

Is your feature request related to a problem? Please describe.

This is not related to a bug with EPPlus, rather to help clarify a difference between Windows and Linux environments.

The documentation specifies that the license info can be set via an environment variable named EPPlusLicense on the machine running the application. Using that exact variable name works as described. However, if the environment variable is named using different case characters than this (ex: EPPLUSLICENSE) in a Linux environment, EPPlus fails to find the environment variable. It is a common convention to name environment variables in all caps in both Windows and Linux environments, so this could trip up other developers (it tripped me up after all).

Describe the solution you'd like

• Small modification to the license documentation stating that if choosing to set the license info via environment variable, to make sure to use the exact correct case for the variable name on Linux, as environment variable names in Linux are case-sensitive.

[JanKallman]

Sure, I'll update our wiki and we will the docs on our web page.