implement post for generic HTTP request - call postXhr

[todo]

NETCoreBlockly/src/NetCore2Blockly/TestBlocklyHtml/wwwroot/blockly/blocklyXHR.js

Lines 31 to 34 in afdcdbd

	//TODO: implement post for generic HTTP request - call postXhr
	throw 'not implemented';
	break;
	}

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This issue was generated by todo based on a TODO comment in afdcdbd. It's been assigned to @ignatandrei because they committed the code.

[ignatandrei]

For the generic XHR block implement POST with - or without - data.