docs: add scarf analytics

[ccmao1130]

Added Scarf pixels and custom telemetry (See: https://docs.scarf.sh/custom-telemetry/) for collecting anonymous user data.

Custom Telemetry has been added to track each runner

Current locations where pixels have been added:

• Daft repo README
• Daft user guide
• Daft API Docs

[codspeed-hq]

CodSpeed Performance Report

Merging #3773 will degrade performances by 22.95%

_{Comparing docs-scarf (86b3377) with main (ca36593)}

Summary

❌ 1 regressions
✅ 26 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	test_iter_rows_first_row[100 Small Files]	167 ms	216.7 ms	-22.95%

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.83%. Comparing base (ca36593) to head (86b3377).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3773   +/-   ##
=======================================
  Coverage   77.82%   77.83%           
=======================================
  Files         745      746    +1     
  Lines       94416    94440   +24     
=======================================
+ Hits        73480    73505   +25     
+ Misses      20936    20935    -1     

Files with missing lines	Coverage Δ
daft/__init__.py	23.68% <ø> (ø)
daft/context.py	84.14% <100.00%> (+0.81%)	⬆️
daft/scarf_telemetry.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes