Implement functions from the reference

[thygesteffensen]

https://learn.microsoft.com/en-us/azure/logic-apps/workflow-definition-language-functions-reference

The following list is the prioritised order based on category:

• Math functions
• Logical comparison functions
• String functions
• Conversion functions
• Implicit data type conversions
• Collection functions
• Date and time functions
• Manipulation functions: JSON & XML
• Workflow functions (might not be applicable?)
• URI parsing functions