[DOCUMENTATION] Add User Documentation for Strategies

[bund5chuh]

Current situation
The documentation needs to be improved. The strategies are a core element of PlatynUI and need a proper documentation from the user perspective.

Describe the solution you'd like
The user documentation has a section that explains the following aspects

• what is a strategy (for PlatynUI)
• list of all the strategies, their purposes, when and how to use them, which controls are available
• examples of usage, screenshots/images to better explain
• provide a working Robot Framework example with a test app (e.g. KeePass, self-written program in python/QT) for each strategy. These examples also serve as acceptance tests for PlatynUI