message: Add a section in the DeveloperGuide about avoiding unsigned integer
diff: @@ -10,6 +10,12 @@ MLIR follows the [LLVM style](https://llvm.org/docs/CodingStandards.html) guide
  except:
  * Adopts [camelBack](https://llvm.org/docs/Proposals/VariableNames.html);
  +* Prefer `int` when possible and use unsigned only for bitmask and when you
  + intend to rely on wrapping behavior. For the rational about this, see
  + [unsigned: A Guideline for Better
  + Code](https://www.youtube.com/watch?v=wvtFGa6XJDU) and [Garbage In,
  + Garbage Out: Arguing about Undefined
  + Behavior...](https://www.youtube.com/watch?v=yG1OZ69H_-o)
  ## Pass name and other command line options
  