Add font family support on bottom tabs (#961)

* Add font family support on bottom tabs

* import missing classes

* import missing class

* update document

android/app/src/main/java/com/reactnativenavigation/params/StyleParams.java

     public boolean forceTitlesDisplay;
     public Color bottomTabBadgeTextColor;
     public Color bottomTabBadgeBackgroundColor;
+    public String bottomTabFontFamily;
 
     public Color navigationBarColor;
 }

android/app/src/main/java/com/reactnativenavigation/params/parsers/StyleParamsParser.java

         result.navigationBarColor = getColor("navigationBarColor", getDefaultNavigationColor());
         result.forceTitlesDisplay = getBoolean("forceTitlesDisplay", getDefaultForceTitlesDisplay());
 
+        result.bottomTabFontFamily = params.getString("bottomTabFontFamily", getDefaultBottomTabFontFamily());
+
         return result;
     }
 
         return AppStyle.appStyle == null ? new StyleParams.Color() : AppStyle.appStyle.statusBarColor;
     }
 
+    private String getDefaultBottomTabFontFamily() {
+        return AppStyle.appStyle == null ? "sans-serif" : AppStyle.appStyle.bottomTabFontFamily;
+    }
+
     private boolean getBoolean(String key, boolean defaultValue) {
         return params.containsKey(key) ? params.getBoolean(key) : defaultValue;
     }

android/app/src/main/java/com/reactnativenavigation/views/BottomTabs.java

 package com.reactnativenavigation.views;
 
 import android.content.Context;
+import android.content.res.AssetManager;
 import android.graphics.Color;
+import android.graphics.Typeface;
 
 import com.aurelhubert.ahbottomnavigation.AHBottomNavigation;
 import com.aurelhubert.ahbottomnavigation.AHBottomNavigationItem;
 import com.reactnativenavigation.params.StyleParams;
 import com.reactnativenavigation.utils.ViewUtils;
 
+import java.io.IOException;
+import java.util.Arrays;
 import java.util.List;
 
 public class BottomTabs extends AHBottomNavigation {
         setId(ViewUtils.generateViewId());
         createVisibilityAnimator();
         setStyle();
+        setFontFamily(context);
     }
 
     public void addTabs(List<ScreenParams> params, OnTabSelectedListener onTabSelectedListener) {
     private boolean hasBadgeBackgroundColor() {
         return AppStyle.appStyle.bottomTabBadgeBackgroundColor != null && AppStyle.appStyle.bottomTabBadgeBackgroundColor.hasColor();
     }
+
+    private boolean hasBottomTabFontFamily() {
+        return AppStyle.appStyle.bottomTabFontFamily != null;
+    }
+
+    private void setFontFamily(Context context) {
+        if(hasBottomTabFontFamily()) {
+
+            AssetManager assetManager = context.getAssets();
+            String fontFamilyName = AppStyle.appStyle.bottomTabFontFamily;
+
+            Typeface typeFace = null;
+            try {
+                boolean hasAsset = Arrays.asList(assetManager.list("fonts")).contains(fontFamilyName);
+                typeFace = hasAsset ?
+                        Typeface.createFromAsset(assetManager, "fonts/".concat(fontFamilyName))
+                        :
+                        Typeface.create(fontFamilyName, Typeface.NORMAL);
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+
+            if(typeFace != null) {
+                setTitleTypeface(typeFace);
+            }
+        }
+    }
 }

docs/styling-the-tab-bar.md

   tabBarButtonColor: '#ffff00', // change the color of the tab icons and text (also unselected)
   tabBarSelectedButtonColor: '#ff9900', // change the color of the selected tab icon and text (only selected)
   tabBarBackgroundColor: '#551A8B' // change the background color of the tab bar
+  tabBarTextFontFamily: 'Avenir-Medium' //change the tab font family
 }
 ```
 
     tabBarBackgroundColor: '#0f2362',
     tabBarButtonColor: '#ffffff',
     tabBarSelectedButtonColor: '#63d7cc'
+    tabFontFamily: 'Avenir-Medium.ttf'  // for asset file or use existing font family name
   },
 ...
 }

src/deprecated/platformSpecificDeprecated.android.js

     forceTitlesDisplay: originalStyleObject.forceTitlesDisplay,
     bottomTabBadgeTextColor: processColor(originalStyleObject.bottomTabBadgeTextColor),
     bottomTabBadgeBackgroundColor: processColor(originalStyleObject.bottomTabBadgeBackgroundColor),
+    bottomTabFontFamily: originalStyleObject.tabFontFamily,
 
     navigationBarColor: processColor(originalStyleObject.navigationBarColor)
   }