Add Beckhoff TwinCAT file support for structured text (st) language

[philippleidig]

Context

• [X] This issue is not a bug report. (please use a different template for reporting a bug)
• [X] This issue is not a duplicate of an existing issue. (please use the search to find existing issues)

Description

Since the automation world is becoming more and more similar to the IT world, it would be of great advantage if the support of the structured text (st) language ( part of IEC 61131-3 ) is extended to the TwinCAT file extensions from Beckhoff Automation.

The structure of the files is almost identical to the previous file extensions "*.st", except for a few minor details.

In addition to ".st", ".TcPOU", ".TcGVL", ".TcDUT" and "*.TcIO" would be added for the TwinCAT files.

See documentation of Beckhoff Automation https://infosys.beckhoff.com/english.php?content=../content/1033/tc3_sourcecontrol/406303499.html&id=4324324478820586350

FUNCTION_BLOCK MyFunctionBlock
VAR_INPUT
	Input : BOOL := TRUE;
END_VAR

VAR_OUTPUT
	Output : LREAL;
END_VAR