Issue #91 Add header offset (#92)

* Remove .DS_Store

* Add optional height offset for header

Author: nholik

.DS_Store

@@ -3,6 +3,8 @@
 ##
 ## Get latest from https://github.com/github/gitignore/blob/master/VisualStudio.gitignore
 
+.DS_Store
+
 # User-specific files
 *.rsuser
 *.suo

.gitignore

@@ -79,6 +79,20 @@ Wrap your root component in `AutocompleteDropdownContextProvider` from `react-na
 </AutocompleteDropdownContextProvider>
 ```
 
+If you have a header component, you can pass an offset.  For example with react navigation 
+
+```js
+//...
+import { useHeaderHeight } from '@react-navigation/elements';
+//...
+const headerHeight = useHeaderHeight();
+//...
+
+<AutocompleteDropdownContextProvider headerOffset={headerHeight} >
+    <AppRootOrWhatever/>
+</AutocompleteDropdownContextProvider>
+```
+
 import the package
 
 ```js

README.md

@@ -20,7 +20,7 @@ export const AutocompleteDropdownContext = React.createContext<IAutocompleteDrop
   activeInputRef: undefined
 })
 
-export const AutocompleteDropdownContextProvider: FC<any> = ({ children }) => {
+export const AutocompleteDropdownContextProvider: FC<any> = ({ headerOffset = 0, children }) => {
   const [content, setContent] = useState<IAutocompleteDropdownContext['content']>()
   const [direction, setDirection] = useState<IAutocompleteDropdownContext['direction']>(undefined)
   const [show, setShow] = useState(false)
@@ -42,14 +42,14 @@ export const AutocompleteDropdownContextProvider: FC<any> = ({ children }) => {
 
     if (dropdownHeight && direction === 'up') {
       setContentStyles({
-        top: inputMeasurements.y - dropdownHeight - 10,
+        top: inputMeasurements.y - dropdownHeight - 10 - headerOffset,
         left: inputMeasurements.x,
         width: inputMeasurements.width
       })
       setOpacity(1)
     } else if (direction === 'down') {
       setContentStyles({
-        top: inputMeasurements.y + inputMeasurements.height + 5,
+        top: inputMeasurements.y + inputMeasurements.height + 5 - headerOffset,
         left: inputMeasurements.x,
         width: inputMeasurements.width
       })