Documentation/applications: add mlearning docs and rename mlearing.

[Abhishekmishra2808]

Summary

• Machine learning applications live in apps/mlearning, but the NuttX docs used the misspelled Documentation/applications/mlearing path and were title-only stubs.
• TensorFlow Lite Micro (apps/mlearning/tflite-micro) and standalone CMSIS-NN had no documentation at all.
• Rename the docs directory to mlearning, document each package from the current Kconfig/Makefiles/tflm_tool.cc, and add the sim:tflm board configuration.

Impact

• Documentation only. No code, Kconfig, or runtime change.
• Existing mlearing doc URLs move to mlearning.

Testing

I confirm that changes are verified on local setup and works as intended:

• Build Host(s): Linux (WSL2), x86_64, GCC 13.3.0
• Target(s): docs Sphinx HTML; sim:tflm Makefile build

Checkpatch on this commit:

$ ./tools/checkpatch.sh -c -u -m -g HEAD~1...HEAD
Used config files:
    1: .codespellrc
✔️ All checks pass.

Sphinx documentation build (Documentation/, warnings as errors):

$ cd Documentation
$ pipenv run make html
Removing everything under '_build'...
Running Sphinx v6.2.1
building [html]: targets for 1683 source files that are out of date
updating environment: [new config] 1678 added, 0 changed, 0 removed
...
checking consistency... done
...
build succeeded.

The HTML pages are in _build/html.

Generated pages include applications/mlearning/index.html and applications/mlearning/tflite-micro/index.html.

sim:tflm configure and Makefile build (original logs):

$ ./tools/configure.sh sim:tflm
  Copy files
  Select CONFIG_HOST_LINUX=y
  Refreshing...
Loaded configuration '.config'
Configuration saved to '.config'

$ make -j$(nproc)
Register: hello
Register: nsh
Register: sh
Register: dd
Register: tflm
...
CXX:  tflm_tool.cc
IN: /home/abhishek/nuttx-apps/libapps.a -> staging/libapps.a
...
LD:  nuttx
Pac SIM with dynamic libs..
SIM elf with dynamic libs archive in nuttx.tgz

[FelipeMdeO]

Hello @Abhishekmishra2808 thank you very much for this PR, It will help me a lot too.