Contributing: Update contributing guide and use Markdown.

CONTRIBUTING.md

@@ -0,0 +1,33 @@
+# Contributing code to Matrix
+
+Please read Synapse [contributing guide](https://github.com/matrix-org/synapse/blob/master/CONTRIBUTING.md).
+
+# Contributing code to Element iOS
+
+## I want to help translating
+
+If you want to fix an issue for an English string, please submit a pull request to the Element iOS GitHub repository.
+If you want to fix an issue for another language, add a missing translation, or  add a new language, please read [Element Web translating guide](https://github.com/vector-im/element-web/blob/develop/docs/translating.md) first and then use the Element iOS [Weblate](https://translate.riot.im/projects/riot-ios/).
+
+If you have any question regarding translations please ask in [Element Translation room](#element-translations:matrix.org).
+
+## Setting up a development environment
+
+Please refer to the [installation guide](INSTALL.md) to setup the project.
+
+## Implement a new screen or new screen flow
+
+New screen flows are currently using MVVM-Coordinator pattern. Please refer to the screen template [Readme](Tools/Templates/README.md) to create a new screen or a new screen flow.
+
+## Coding style
+
+For Swift coding style we use [SwiftLint](https://github.com/realm/SwiftLint) to check some conventions at compile time (rules are located in the `.swiftlint.yml` file). 
+Otherwise please have a look to [Apple Swift conventions](https://swift.org/documentation/api-design-guidelines.html#conventions). We are also using some of the conventions of [raywenderlich.com Swift style guide]([https://github.com/raywenderlich/swift-style-guide).
+
+## Pull request
+
+When you are making a pull request please read carefully the [Pull Request Checklist](https://github.com/vector-im/element-ios/blob/develop/.github/PULL_REQUEST_TEMPLATE.md).
+
+## Thanks
+
+Thanks for contributing to Matrix projects!

Tools/Templates/README.md

@@ -3,7 +3,7 @@ The `buildable` folder contains templates with source files that build.
 The goal is to turn these templates as Xcode templates. They are part of the Riot project in order to ensure they build
 
 # ScreenTemplate
-This is the boilerplate to create a screen that follows the MVVM-C pattern used within the Riot app.
+This is the boilerplate to create a screen that follows the MVVM-C pattern used within the Element app.
 
 To create a screen from this template (before it becomes an Xcode template):