Nuclick (#1094)

Fixes # .
- Tutorials for NuClick + Nuclei classification
- Fix headings format in README.md

### Description
Notebooks for infer + train for both nuclick and classification models.

Easy to visualize:
https://github.com/SachidanandAlle/tutorials/tree/nuclick

https://github.com/SachidanandAlle/tutorials/tree/nuclick/pathology/nuclick

### Checks
<!--- Put an `x` in all the boxes that apply, and remove the not
applicable items -->
- [x] Notebook runs automatically `./runner [-p <regex_pattern>]`

Signed-off-by: Sachidanand Alle <[email protected]>

Author: SachidanandAlle

README.md

@@ -0,0 +1,29 @@
+# Nuclick and Classification Examples
+This folder contains examples to run train and validate a nuclick and classification models.
+It also has notebooks to run inference over trained (monai-zoo) model.
+
+### 1. Data
+
+Training these model requires data. Some public available datasets which are used in the examples can be downloaded from [ConSeP](https://warwick.ac.uk/fac/cross_fac/tia/data/hovernet).
+
+### 2. Questions and bugs
+
+- For questions relating to the use of MONAI, please us our [Discussions tab](https://github.com/Project-MONAI/MONAI/discussions) on the main repository of MONAI.
+- For bugs relating to MONAI functionality, please create an issue on the [main repository](https://github.com/Project-MONAI/MONAI/issues).
+- For bugs relating to the running of a tutorial, please create an issue in [this repository](https://github.com/Project-MONAI/Tutorials/issues).
+
+### 3. List of notebooks and examples
+
+#### NuClick Interaction Model
+#### [Training](./nuclick_training_notebook.ipynb)
+This notebook guides to train a NuClick model.
+
+#### [Inference](./nuclick_infer.ipynb)
+This notebook guides to segment a nuclei for given user click(s).
+
+#### Nuclei Classification Model
+#### [Training](./nuclei_classification_training_notebook.ipynb)
+This notebook guides to train a classification model for certain nuclei types.
+
+#### [Inference](./nuclei_classification_infer.ipynb)
+This notebook helps to infer classification model for a given Nulei.