1. fixed an issue that stopped us from running Raindrop on multiple CUDA devices;
2. added Mean and Median as naive imputation methods;

What's Changed

• Refactor LOCF, fix Raindrop on multiple cuda devices, and update docs by @WenjieDu in #308
• Remind how to display the figs rather than invoking plt.show() by @WenjieDu in #310
• Update the docs and requirements by @WenjieDu in #311
• Fixing some bugs, updating the docs and requirements by @WenjieDu in #312
• Make CI workflows only test with Python v3.7 and v3.11 by @WenjieDu in #313
• Update the docs and release v0.3.2 by @WenjieDu in #314
• Add mean and median as imputation methods, and update docs by @WenjieDu in #317

Full Changelog: v0.3.1...v0.3.2