😊🔵𝐒 Improve GameStudio's About window

[Kryptos-FR]

The MIT License and See the list links in the About window open the files LICENSE.md and THIRD PARTY.md respectively using a system process. However it will not work properly if the user hasn't associated the .md file extension with a text editor (for instance).

Instead, it should open a popup Window where the content of those files is rendered (using a markdown plugin).