added docs for KSR.textopsx.bl_iterator_value(...)

kamailio-kemi-framework/docs/modules/textopsx/textopsx.bl_iterator_value.md

@@ -0,0 +1,3 @@
+Return the content of the body line for the current position of the cursor, including the EoL.
+
+It is an alternative to getting the line content via `$blitval(iname)`.