Update Read_me (#201)

Add know issue and workaround in ios

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Co-authored-by: m0nac0 <58807793+m0nac0@users.noreply.github.com>

README.md

@@ -151,6 +151,18 @@ buildTypes {
 
 Please include the `NSLocationWhenInUseUsageDescription` as described [here](#location-features)
 
+### Layer is not displayed on IOS, but no error
+
+Have a look in your `LayerProperties` object, if you supply a `lineColor` argument, (or any color argument) the issue might come from here.
+Android supports the following format : `'rgba(192, 192, 255, 1.0)'`,  but on iOS, this doesn't work! 
+
+You have to have the color in the following format : `#C0C0FF` 
+
+### iOS crashes with error: `'NSInvalidArgumentException', reason: 'Invalid filter value: filter property must be a string'`
+Check if one of your expression is : `["!has", "value"]`. Android support this format, but iOS does not.
+You can replace your expression with :   `["!",["has", "value"] ]` which works both in Android and iOS.
+
+Note : iOS will display the error : `NSPredicate: Use of 'mgl_does:have:' as an NSExpression function is forbidden`, but it seems like the expression still works well.
 
 ## Contributing