docs: add readme

.gitignore

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 data/*
-output/*
+output/*
+*.pth
+__pycache__/*
+*.pyc

README.md

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+# DDPM
+
+A Simple implementation of DDPM model in PyTorch.
+
+![](./images/Screenshot_20230314_225320.png)
+![](./images/ezgif.com-gif-maker.gif)
+
+## Traning
+
+Before training, please set up the config.ini file:
+
+```ini
+[unet]
+batch_size = 256
+time_emb_dim = 128
+device = cuda
+epoch_num = 500
+learning_rate = 1e-4
+
+[ddpm]
+iteration = 500
+```
+
+To start training, run:
+
+```
+$ python train.py
+```
+
+## Sampling
+
+To generate 16 pictures, run the following command:
+
+The pictures will be output to the `./output` directory.
+
+```
+$ python sample 16
+```