Ssqueezepy

Updated deprecated CuPy method.

For all changes, see [CHANGELOG](https://github.com/OverLordGoldDragon/ssqueezepy/blob/master/CHANGELOG.md).

See [CHANGELOG](https://github.com/OverLordGoldDragon/ssqueezepy/blob/master/CHANGELOG.md).

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`

Dramatic speed and memory improvements, along other changes; see [changelog](https://github.com/OverLordGoldDragon/ssqueezepy/blob/master/CHANGELOG.md).

Adds a DOI for citation purposes

- Short-time Fourier Transform, forward & inverse
- STFT-based synchrosqueezing, forward & inverse
- Generalized Morse Wavelets

**Existing users**: please review code anew; too many changes to note between Prerelease 2 and v0.5.0. This changes onward, with every change explicitly tracked.