various docs updates

docs/reference/logic.md

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+# Logic
+
+[if](/microbit/reference/logic/if)
+
+```blocks
+if(true) {
+}
+```
+
+[Boolean](/microbit/reference/types/boolean) values: *true*; *false*
+
+```blocks
+true
+false
+```
+
+Boolean binary operators: *and* (conjunction); *or* (disjunction)
+
+```blocks
+true && false;
+true || false;
+```
+
+Boolean negation operator
+
+```blocks
+!true
+```
+
+Comparison operators (=, !=, <, >, <=, >=)
+
+```blocks
+0 == 0;
+1 !- 0;
+0 < 1;
+1 > 0;
+0 <= 1;
+1 >= 0;
+```