KWYG 23 coding guidelines erstellen (#12)

* V.1 coding guidelines for typescript project.
* Resolves #6

CodingGuidelines.md

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+# Coding Guidelines - React Typescript
+
+## Names
+1. Do not use "_" as a prefix for private properties.
+2. Use whole words in names when possible.
+3. Give folders/files/components/functions unique names.
+
+Style | Category
+--- | ---
+PascalCase | class / enum / decorator / component files
+camelCase | variable / parameter / function / method / property / module alias / folder names + non-component files
+CONSTANT_CASE | global constant values (declared on module level; if the value can be instantiated more than once it must use camelCase) 
+
+## Components
+1. 1 file per logical component.
+2. Filename should match the component name.
+
+## `null` and `undefined`
+1. Use **undefined**. Do not use null.
+
+## Comments
+1. Use JSDoc-style comments (`/** JSDoc */`) for functions, interfaces, enums, and classes.
+   1. Specify all function attribute/parameter types
+   2. Only specify function attributes/parameters with text if they are not self-explanatory.
+2. Use single line comments (`// line comment`) for implementation comments.
+3. Write comments only if they add value. Do not comment for the sake of commenting.
+   > What comments are needed so that another developer understands the code?<br/>
+   > Keep in mind: The comments are the projects documentation. If the code is not self-explanatory, it should be refactored/commented. 
+
+## Style
+1. Use arrow functions over anonymous function expressions.
+2. Only surround arrow function parameters when necessary.<br/>
+   For example, `(x) => x + x` is wrong but the following are correct:
+   1. `x => x + x`
+   2. `(x, y) => x + y`
+   3. `<T>(x: T, y: T) => x === y`
+3. Always surround loop and conditional bodies with curly braces. Statements on the same line are allowed to omit braces.
+4. Open curly braces always go on the **same line** as whatever necessitates them.
+5. Use a single declaration per variable statement (i.e. use `var x = 1; var y = 2;` over `var x = 1, y = 2;`).
+6. Separate function from the JSX if it takes more than one line (i.e. button click).
+7. Do not use inline styles. Use separate CSS files instead.
+8. Use 2 spaces for indentation.
+   > VSCode: *View* -> *Command Palette...* -> *"Indent Using Spaces"* ->  **2**
+
+## Structure within components
+1. Imports - Prefer destructuring over importing the whole module.
+2. Additional variables
+3. Component/Class
+   1. Optional constructor
+      > Only use constructor if you need to set initial state or bind methods. JavaScript will automatically create an empty constructor for you.
+   2. Definitions
+   3. Functions
+   4. Additional destructors
+4. Exports