text: Title: Add Flower Baseline: FedDefender
  Body: ### Paper
  
  Gill, Waris and Anwar, Ali and Gulzar, Muhammad Ali(2023) - FedDefender: Backdoor Attack Defense in Federated Learning
  
  ### Link
  
  https://arxiv.org/abs/2307.08672
  
  ### Maybe give motivations about why the paper should be implemented as a baseline.
  
  FedDefender is a defense against backdoor attacks in federated learning by leveraging differential testing for FL. FedDefender minimizes the impact of a malicious client on the global model by limiting its contribution to the aggregated global model. FedDefender fingerprints the neuron activations of clients’ models on the same input and uses differential testing to identify potential malicious clients. 
  
  ### Is there something else you want to add?
  
  _No response_
  
  ### Implementation
  
  #### To implement this baseline, it is recommended to do the following items in that order:
  
  ### For first time contributors
  
  - [x]  Read the [`first contribution` doc](https://flower.ai/docs/first-time-contributors.html)
  - [ ]  Complete the Flower tutorial
  - [x]  Read the Flower Baselines docs to get an overview:
      - [x]  [How to use Flower Baselines](https://flower.ai/docs/baselines/how-to-use-baselines.html)
      - [x]  [How to contribute a Flower Baseline](https://flower.ai/docs/baselines/how-to-contribute-baselines.html)
  
  
  ### Prepare - understand the scope
  
  - [X] Read the paper linked above
  - [X] Decide which experiments you'd like to reproduce. The more the better!
  - [X] Follow the steps outlined in [Add a new Flower Baseline](https://flower.ai/docs/baselines/how-to-contribute-baselines.html#add-a-new-flower-baseline).
  - [X] You can use as reference [other baselines](https://github.com/adap/flower/tree/main/baselines) that the community merged following those steps.
  
  ### Verify your implementation
  
  - [ ] Follow the steps indicated in the `EXTENDED_README.md` that was created in your baseline directory
  - [ ] Ensure your code reproduces the results for the experiments you chose
  - [ ] Ensure your `README.md` is ready to be run by someone that is no familiar with your code. Are all step-by-step instructions clear?
  - [ ] Ensure running the formatting and typing tests for your baseline runs without errors.
  - [ ] Clone your repo on a new directory, follow the guide on your own `README.md` and verify everything runs.