Fix typo in README (#19)

Author: hayatoikoma

README.md

@@ -38,7 +38,7 @@ The LinearMaps package provides the following functionality:
 
     ```
     LinearMap{T}(A::AbstractMatrix[; issymmetric::Bool, ishermitian::Bool, isposdef::Bool])
-    LinearMap{T}(A::LinearMap[; issym::Bool, ishermitian::Bool, isposdef::Bool])
+    LinearMap{T}(A::LinearMap[; issymmetric::Bool, ishermitian::Bool, isposdef::Bool])
     ```
 
     Create a `WrappedMap` object that will respond to the methods `issymmetric`, `ishermitian`, `isposdef` with the values provided by the keyword arguments, and to `eltype` with the value `T`. The default values correspond to the result of calling these methods on the argument `A`; in particular `{T}` does not need to be specified and is set as `eltype(A)`. This allows to use an `AbstractMatrix` within the `LinearMap` framework and to redefine the properties of an existing `LinearMap`.