Added extended scalar blog entry

content/blog/introducing-extended-scalars.md

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+title = "Introducing graphql-java-extended-scalars"
+author = "Brad Baker"
+tags = []
+categories = []
+date = 2018-11-24T01:00:00+10:00
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+
+One of the most common questions we get in GraphQL Java land is "can we have a datetime scalar".
+
+This is not defined by the graphql specification per se so we are reluctant to add it to the core library and then have it turn
+up later as an officially specified type.
+
+But it really is a badly needed type in your GraphQL arsenal and hence `graphql-java-extended-scalars` was born 
+
+https://github.com/graphql-java/graphql-java-extended-scalars
+
+This will be a place where we can add non standard but useful extensions to GraphQL Java.
+
+The major scalars we have added on day one are
+
+ * The aforementioned DateTime scalar as well as a Date and Time scalar
+ * A Object scalar or sometimes know as a JSON scalar that allows a map of values to be returned as a scalar value
+ * Some numeric scalars that constrain the values allowed such as `PositiveInt`
+ * A Regex scalar that allows a string to fit a regular expression
+ * A Url scalar that produces `java.net.URL` objects at runtime 
+ * And finally an aliasing technique that allows you to create more meaningfully named scalar values
+
+ We hope you find them useful. 
+
+
+Cheers,<br>
+Brad