Usage example demo: custom report builder

[sequba]

Create strackblitz demo that:

• shows data as a table
• demonstrates the power of named expressions
• allows to set custom names for data columns
• allows to calculate math and statistical expressions using the human-friendly column names

Link this demo to the documentation and repo readme to "What HyperFormula can be used for?" section:

[warpech]

The best name we have for this demo is Custom report builder

I think this demo could have e.g.

• 6 normal columns of 3 different data types (the columns should be referred to by name, not by "A1" address)
• 3 calculated columns that use editable formulas
  • one per each data type
  • for the purpose of this demo, it is OK if the formula editors are plain textareas
• 1 derived calculated column that uses the result of calculated columns