[onert-micro] Release Note for 2.0.0-pre (#13334)

- Release Note for onert-micro 2.0.0-pre

ONE-DCO-1.0-Signed-off-by: Chunseok Lee <chunseok.lee@samsung.com>

docs/release/onert-micro/2.0/release-note-2.0.0-pre.md

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+## Release Notes for onert-micro 2.0.0-pre 
+
+### Overall Structure Refactored
+
+- c++ api has been changed : [onert-micro c++ api](https://github.com/samsung/ONE/blob/master/onert-micro/onert-micro/include/OMInterpreter.h)
+- 60 ops supported : Abs, Add, AddN, AveragePool2D, ArgMax, ArgMin, Concatenation, BatchToSpaceD, Cos, Div, DepthwiseCov2D, Dequatize, FullyCoected, Cov2D, Logistic, Log, Gather, GatherD, Exp, Greater, GreaterEqual, ExpadDims, Equal, Floor, FloorDiv, FloorMod, Pad, Reshape, ReLU, ReLU6, Roud, Less, L2ormalize, L2Pool2D, LessEqual, LeakyReLU, LogSoftmax, Mul, Maximum, MaxPool2D, Miimum, otEqual, Si, SquaredDifferece, Slice, Sub, Split, SpaceToBatchD, StridedSlice, Square, Sqrt, SpaceToDepth, Tah, Traspose, TrasposeCov, Softmax, While, Rsqrt, Upack
+
+### onert-micro supports on-device training feature
+
+- Trainable Operations : 5 operations ( Conv2D, FullyConnected, MaxPool2D, Reshape, Softmax )
+- Loss : MSE, Categorical Cross Entropy
+- Optimizer : ADAM, SGD
+- C api for training feature : [onert-micro c api header](https://github.com/samsung/ONE/blob/master/onert-micro/onert-micro/include/onert-micro.h)
+- limitation : For now, you can train topologically linear model