Update gitignore and add code style guidelines in CONTRIBUTING.md

.gitignore

@@ -31,6 +31,7 @@ bld/
 [Oo]bj/
 [Ll]og/
 [Ll]ogs/
+[Oo]ut/
 
 # Visual Studio 2015/2017 cache/options directory
 .vs/

CONTRIBUTING.md

@@ -0,0 +1,50 @@
+# Stability Matrix Code Style Guidelines
+These are just guidelines, mostly following the official C# style guidelines, except in a few cases. We might not adhere to these 100% ourselves, but lets try our best :)
+
+## Naming conventions
+#### Pascal Case
+- Use pascal casing ("PascalCasing") when naming a `class`, `record`, `struct`, or `public` members of types, such as fields, properties, methods, and local functions.
+- When naming an `interface`, use pascal casing in addition to prefixing the name with the letter `I` to clearly indicate to consumers that it's an `interface`.
+#### Camel Case
+- Use camel casing ("camelCasing") when naming `private` or `internal` fields.
+- **Do not** prefix them with an underscore `_`
+## `using` Directives
+- Please do not check in code with unused using statements.
+## File-scoped Namespaces
+- Always use file-scoped namespaces. For example:
+```csharp
+using System;
+
+namespace X.Y.Z;
+
+class Foo
+{
+}
+```
+## Implicitly typed local variables
+- Use implicit typing (`var`) for local variables when the type of the variable is obvious from the right side of the assignment, or when the precise type is not important.
+
+## Optional Curly Braces
+- Only omit curly braces from `if` statements if the statement immediately following is a `return`. 
+
+For example, the following snippet is acceptable:
+```csharp
+if (alreadyAteBreakfast)
+    return;
+```
+
+Otherwise, it must be wrapped in curly braces, like so:
+```csharp
+if (alreadyAteLunch)
+{
+    mealsEaten++;
+}
+```
+
+## Project Structure
+- Try to follow our existing structure, such as putting model classes in the `Models\` directory, ViewModels in `ViewModels\`, etc.
+- Static classes with only extension methods should be in `Extensions\`
+- Mock data for XAML Designer should go in `DesignData\`
+- The `Helper\` and `Services\` folder don't really have guidelines, use your best judgment
+- XAML & JSON converters should go in the `Converters\` and `Converters\Json\` directories respectively
+- Refit interfaces should go in the `Api\` folder