Update documentation

CONTRIBUTING.md

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+# Contributing
+
+> #### Table of Contents
+> - [Running Locally](#running-locally)
+> - [Directory Structure](#directory-structure)
+
+Are you a first-timer in contributing to open source? [These guidelines](https://opensource.guide/how-to-contribute/#how-to-submit-a-contribution) from GitHub might help!
+
+## Running Locally
+
+1. Fork this repository.
+
+2. Clone your forked repo to your machine.
+
+    ```bash
+    git clone https://github.com/<your-username>/server.git    
+    ```
+
+3. Install [Docker](https://docs.docker.com/install/), if not done already.
+
+4. Install dependencies, and run the server.
+
+    ```bash
+    cd server
+
+    npm install
+    
+    npm run watch
+    ```
+    
+5. Open [`http://localhost:8080/`](http://localhost:8080/) in a web browser.
+
+## Directory Structure
+
+- [**src/**](src) contains source code. 
+    - [**config/**](src/config) contains configuration files.
+    - [**controllers/**](src/controllers) routes and processes incoming requests.
+    - [**middlewares/**](src/middlewares) contains Express middlewares.
+    - [**models/**](src/models) manages algorithm visualizations and their hierarchy.
+    - [**tracers/**](src/tracers) build visualization libraries and compiles/runs code.
+    - [**utils/**](src/utils) contains utility files.
+
+**NOTE** that for JavaScript, it builds a web worker rather than a docker image. Once a browser fetches the web worker, it will submit users' code to the web worker locally, instead of submitting to the remote server, to extract visualizing commands.

README.md

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+# Server
+
+> This repository is part of the project [Algorithm Visualizer](https://github.com/algorithm-visualizer).
+
+`server` serves [`algorithm-visualizer`](https://github.com/algorithm-visualizer/algorithm-visualizer) and provides APIs that the web app needs on the fly. (e.g., GitHub sign in, compiling/running code, etc.)
+
+## Contributing
+
+Check out the [contributing guidelines](https://github.com/algorithm-visualizer/algorithms/blob/master/CONTRIBUTING.md).