doc: intro guide to vortex

[ptravers]

closes: #3996

[joseph-isaacs]

The md rendering looks a little wrong here.

[ptravers]

will take a look! thanks!

[blaginin]

сс @connortsui20 as you worked on docs improvements recently too

[codecov]

Codecov Report

❌ Patch coverage is 0% with 684 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.41%. Comparing base (487e8ce) to head (9846812).
⚠️ Report is 107 commits behind head on develop.

Files with missing lines	Patch %	Lines
vortex/examples/array_iteration.rs	0.00%	123 Missing ⚠️
vortex/examples/file_io.rs	0.00%	116 Missing ⚠️
vortex/examples/struct_arrays.rs	0.00%	107 Missing ⚠️
vortex/examples/array_immutability.rs	0.00%	88 Missing ⚠️
vortex/examples/core_concepts.rs	0.00%	60 Missing ⚠️
vortex/examples/debug_printing.rs	0.00%	55 Missing ⚠️
vortex/examples/advanced_array_types.rs	0.00%	54 Missing ⚠️
vortex/examples/string_arrays.rs	0.00%	54 Missing ⚠️
vortex/examples/basic_array_creation.rs	0.00%	27 Missing ⚠️

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