Added docs for setting up executorch on windows

[nil-is-all]

Summary

First documentation for setting up ExecuTorch for Windows and exporting MobileNet V2 model and executing.
This version works only on Windows Powershell on admin mode.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/11273

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

✅ You can merge normally! (1 Unrelated Failure)

As of commit 21e2e99 with merge base ceaf147 ():

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / test-llama-runner-qnn-linux (fp32, qnn_16a16w, qnn) / linux-job (gh) (matched linux rule in flaky-rules.json)
  The process '/usr/bin/git' failed with exit code 128

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[nil-is-all]

@pytorchbot label "release notes: none"

[nil-is-all]

@GregoryComer @SS-JIA Feel free to tag anyone else as well to help review this draft on Windows Doc

[mergennachin]

Why is this a completely different page?

Can we do cards where you can toggle between different codeblocks based on platform

See https://docs.pytorch.org/torchrec/setup-torchrec.html#installation as an example where you can toggle based (pypi, nightly, build from source)

cc @GregoryComer

[SS-JIA]

Awesome stuff!

[mergennachin]

See my previous comment

cc @SS-JIA

[GregoryComer]

Why is this a completely different page?

Can we do cards where you can toggle between different codeblocks based on platform

See https://docs.pytorch.org/torchrec/setup-torchrec.html#installation as an example where you can toggle based (pypi, nightly, build from source)

cc @GregoryComer

@nil-is-all I'll defer to Mergen's preference on where to put this. Can you take a look at trying to integrate into the existing Building from Source page? The code is in using-executorch-building-from-source.md.

We can probably just add a Windows section initially, and we can look at maybe integrating sphinx-tabs or something eventually. There's enough Windows specific steps that I'm fine with having a dedicated windows heading for now.

[nil-is-all]

@GregoryComer I reflected the smaller edits you mentioned. Will work on integrating into the Building from Source page as a section.

[nil-is-all]

@mergennachin, @GregoryComer Added as a section under using-executorch-building-from-source.md
Do let me know if this edit works, with respect to formatting especially.