Manually sync'd code from upstream TF. (#2)

Confirmed that the following command passes:
```
./tensorflow/lite/micro/tools/ci_build/test_all_new.sh GITHUB_PRESUBMIT
```
729 files changed
tree: fb911289e4c82c3e28896ebaab7560785078f0ae
  1. tensorflow/
  2. third_party/
  3. .bazelrc
  4. .gitignore
  5. AUTHORS
  6. CODEOWNERS
  7. CONTRIBUTING.md
  8. LICENSE
  9. README.md
  10. WORKSPACE
README.md

TensorFlow Lite for Microcontrollers

The TFLM code is currently in the process of being refactored out of the Tensorflow github repository into a standalone repo. This refactoring is currently in the initial stages and is expected to be completed towards the end of June 2021.