docs: add --dev flag to book

[Sabnock01]

Adds the --dev flag for reth node to the book. Resolves #3903

[codecov]

Codecov Report

Merging #4307 (5c8bec3) into main (07a1af8) will decrease coverage by 0.03%.
Report is 6 commits behind head on main.
The diff coverage is n/a.

see 10 files with indirect coverage changes

Flag	Coverage Δ
integration-tests	16.83% <ø> (-0.01%)	⬇️
unit-tests	63.75% <ø> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
reth binary	26.12% <ø> (ø)
blockchain tree	82.56% <ø> (ø)
pipeline	90.07% <ø> (ø)
storage (db)	74.77% <ø> (ø)
trie	94.85% <ø> (ø)
txpool	48.20% <ø> (ø)
networking	77.46% <ø> (-0.03%)	⬇️
rpc	58.80% <ø> (-0.09%)	⬇️
consensus	63.53% <ø> (ø)
revm	32.01% <ø> (ø)
payload builder	6.82% <ø> (ø)
primitives	86.14% <ø> (-0.03%)	⬇️

[rkrasiuk]

lgtm! unrelated: @mattsse any reason these are in snake_case (consistency snob here)? any objections to renaming to kebab-case?

[mattsse]

ref #4314