feat: Add reconnection capability for persisted WebDriver sessions

[surajk-m]

Closes #57

The with_existing_session method introduces the ability to reconnect to an already established WebDriver session using its session ID. This enables reuse of an active session without having to create a new one, which is particularly beneficial in scenarios such as process restarts or unexpected disconnections.

[codecov]

Codecov Report

Attention: Patch coverage is 76.11940% with 16 lines in your changes missing coverage. Please review.

Project coverage is 62.94%. Comparing base (29bbfa7) to head (e15af90).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/client.rs	0.00%	13 Missing ⚠️
src/session.rs	94.44%	3 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
src/session.rs	75.03% <94.44%> (+1.44%)	⬆️
src/client.rs	63.06% <0.00%> (-0.75%)	⬇️

... and 3 files with indirect coverage changes

[jonhoo]

This is a great addition, thank you! Just a few smaller bits to tidy up.

[jonhoo]

Looking quite good now, really just nits left :)

[jonhoo]

Excellent, thank you!