restructuring to separate language from API

docs/blocks/variables.md

@@ -0,0 +1,21 @@
+## Variables
+
+[Assign](/blocks/variables/assign) (set) a variable's value
+
+```blocks
+let x = 0;
+```
+
+Get a variable's value
+
+```blocks
+let x = 0;
+x;
+```
+
+[Change](/blocks/variables/change-var) a variable's value
+
+```blocks
+let x = 0;
+x+=1;
+```