Add Sprinzl coordinates for phage T4 and T5 tRNAs

Add data-raw/sprinzl.R, a CM-based Sprinzl position assigner that
aligns tRNA sequences against the tRNAscan-SE bacterial covariance
model and assigns canonical Sprinzl positions based on the CM
consensus structure. Handles D-loop insertions (17a, 20a, 20b),
variable arm e-positions for type II tRNAs, and the standard
cloverleaf numbering system.

Generated coords for 8 T4 phage tRNAs (from test data FASTA) and
5 T5 phage tRNAs (sequences extracted from MODOMICS).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jayhesselberth