MetaModules, TasksetSampler, Adapters & LoRA, more examples and tutorials

Added

• New vision example: MAML++. (@Theo Morales)
• Add tutorial: "Demystifying Task Transforms", (Varad Pimpalkhute)
• Add l2l.nn.MetaModule and l2l.nn.ParameterTransform for parameter-efficient finetuning.
• Add l2l.nn.freezeand l2l.nn.unfreeze.
• Add Adapters and LoRA examples.
• Add TasksetSampler, compatible with PyTorch's Dataloaders.

Changed

• Documentation: uses mkdocstrings instead of pydoc-markdown.
• Remove text/news_topic_classification.py example.
• Rename TaskDataset to Taskset.

Fixed

• MAML Toy example. (@Theo Morales)
• Example for detach_module. (Nimish Sanghi)
• Loading duplicate FGVC Aircraft images.
• Move vision datasets to Zenodo. (mini-ImageNet, tiered-ImageNet, FC100, CIFAR-FS, CUB200)
• mini-ImageNet targets are now ints (not np.float64).
• Swap family for variants in FGVCAircraft, as in MetaDataset.