feat(navbar): readme added (#8)

src/lib/navbar/README.md

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+# Navbar component
+
+## Objectives
+
+-   create the navbar component
+-   create child components to get them included into it
+
+## Allowed child components
+
+We strongly recommend adhere to use our child components until it is possible but you are free to insert there what you want.
+
+ - left\right side container **mc-navbar-section**
+   - product\company title **mc-navbar-brand**
+   - logo container **mc-navbar-logo**
+     - any markup
+       - **mc-navbar-title** (please see below)
+	 - title **mc-navbar-title**
+	   - any markup, only font size, font color, font family is gonna be styled
+	- menu item container **mc-navbar-item**
+	  - icon **[mc-icon]** (another PT Mosaic component, out of the scope of this)
+	  - title **mc-navbar-title**
+    - dropdown **[mc-dropdown]** (another PT Mosaic component, out of the scope of this)
+	  - any markup
+	- any markup
+- any markup
+
+## States
+
+We believe you are able to manage navbar child components from outside. Meantime we provide number of mc-navbar-item states based on css classes which may be combined between each others.
+
+ - mc-navbar-item-active - selected item
+ - mc-progress - something in progress (striped animation)
+ - cdk-focused - focused state, we control it as well for common tab order behaviour
+
+Disable state also could be combined with other states but it is **disabled** attribute.
+
+## Collapsing
+In the case that absence of space the following elements is collapsed:
+
+-  mc-navbar-item is collapsed to [mc-icon] if exists (if not then the item is not collapsed). The title attribute is added for [mc-icon] from mc-navbar-item's [collapsedTitle] input value;
+-  mc-navbar-item is collapsed to [mc-icon] if exists (if not then the item is not collapsed).