Improve documentation for developing

Move existing documentation to `docs/development.md` to have simpler
`README.md` but more dedicated and extensive documentation for
development.

Improve existing documentation for different commands for the project.

Document VSCode recommendations in `extensions.json` file and add
exception in `.gitignore` to be able to add it to repository.

docs/development.md

@@ -0,0 +1,51 @@
+# Development
+
+Before your commit, a good practice is to:
+
+1. [Run unit tests](#testing)
+2. [Lint your code](#linting)
+
+You could run other types of tests as well, but they may take longer time and overkill for your changes. All tests are executed inside a pull request.
+
+## Commands
+
+### Prerequisites
+
+- Install node >15.x.
+- Install dependencies using `npm install`.
+
+### Testing
+
+- Run unit tests: `npm run test:unit`
+- Run integration tests: `npm run test:integration`
+- Run e2e (end-to-end) tests
+  - Interactive mode with GUI: `npm run test:e2e`
+  - Headless mode without GUI: `npm run test:e2e -- --headless`
+
+### Linting
+
+- Lint all (recommended 💡): `npm run lint`
+- Markdown: `npm run lint:md`
+- Markdown consistency `npm run lint:md:consistency`
+- Markdown relative URLs: `npm run lint:md:relative-urls`
+- JavaScript/TypeScript: `npm run lint:eslint`
+- Yaml: `npm run lint:yaml`
+
+### Running
+
+- Run in local server: `npm run serve`
+  - 💡 Meant for local development with features such as hot-reloading.
+- Run using Docker:
+  1. Build: `docker build -t undergroundwires/privacy.sexy:latest .`
+  2. Run: `docker run -it -p 8080:80 --rm --name privacy.sexy undergroundwires/privacy.sexy:latest`
+
+### Building
+
+- Build web application: `npm run build`
+- Build desktop application: `npm run electron:build`
+
+## Recommended extensions
+
+You should use EditorConfig to follow project style.
+
+For Visual Studio Code, recommended extensions are defined in [`.vscode/extensions.json`](./../.vscode/extensions.json).