Add EO to Github linguist

[mximp]

There is a list which is used in Github to detect and highlight syntax of programming languages.
Let's add EO there.

[mximp]

According to the instructions language grammar needs to be specified in Atom/TextMate format: https://github.com/github/linguist/blob/master/CONTRIBUTING.md#adding-a-language

[mximp]

Installation note (Mac OS)

Issue on MacOS: charlock_holmes failed to be installed due to "invalid suffix on literal" error.
Fix: as per brianmario/charlock_holmes#146 directly add spaces into file: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.3.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/include/ruby-2.6.0/universal-darwin21/ruby/config.h

[mximp]

Installation note (Mac OS)

In case script/add-grammar fails complaining to Docker, then additional steps are required:

brew install virtualbox 
brew install docker  
open -a Docker

[mximp]

PR to linguist has been rejected (see comment) due to lack of language popularity (usage by users on GitHub).
PR will be hanging in pending popularity state until criteria is met.