ieegio 0.1.0

• Added burn_curve to burn electrode trajectories (e.g. depth/sEEG leads or DBS shafts) into a volume given start and end positions in image native RAS coordinates, with configurable radius and per-segment colors
• Added a merge mode to burn_curve so newly burned trajectories can be composted onto an existing volume instead of overwriting it
• Added a base R graphics plot method for ieegio_surface objects as an alternative to the default r3js rendering, useful for static figures and environments without WebGL
• Fixed get_channel so channels can be looked up by label (in addition to index) for BCI2000 and BrainVision formats
• Fixed mat_to_quaternion to correctly handle handedness changes, aligning the quaternion sign convention with FreeSurfer
• Code style and lint cleanup across the package; rebuilt documentation