QoL, cleanups, fixes

FEATURES

• freq_to_scale & scale_to_freq, experimental
• Improved auto-scales
• Optional nan_checks
• Improved default gamma

BREAKING

• ssq_freqs now correctly maps frequencies to corresponding rows of Tx for ssq_cwt, no longer requiring [::-1]
• scales returned as 1D
• extract_ridges: ridge_f (formerly fridge) now returns scales rather than log(scales)
• extract_ridges: renamed: fridge -> ridge_f, max_energy -> ridge_e

FIXES

• False warning for t & fs
• Extended scope of astensor to scales, ssq_freqs
• visuals: improve xticks & yticks handling

MISC

• Added citation; README changes; docs changes
• experimental: remove phase_squeeze, phase_transform
• visuals.imshow: default cmap='turbo'
• visuals: added auto_xlims, squeeze