Update data types doc (#3957)

* Update data types docs

* Move alias type to its own section

docs/user-manual/overview/05-enum-arr-ser.md

@@ -15,6 +15,7 @@ system unless otherwise noted. Included in this document:
     - [Arrays](#arrays)
     - [Serializables](#serializables)
     - [C++ Classes](#c-classes)
+  - [Alias Types](#alias-types)
   - [Conclusion](#conclusion)
 
 ## Primitive Types
@@ -29,9 +30,11 @@ following table and are available to both the ground system, events, channels, a
 | I8      | int8_t     | signed 8-bit integer    |
 | I16     | int16_t    | signed 16-bit integer   |
 | I32     | int32_t    | signed 32-bit integer   |
+| I64     | int64_t    | signed 64-bit integer   |
 | U8      | uint8_t    | unsigned 8-bit integer  |
 | U16     | uint16_t   | unsigned 16-bit integer |
 | U32     | uint32_t   | unsigned 32-bit integer |
+| U64     | uint64_t   | unsigned 64-bit integer |
 | F32     | float      | 32-bit floating point   |
 | F64     | double     | 64-bit floating point   |
 
@@ -116,6 +119,13 @@ arbitrary C++ `class`/`struct` types. If these types are to be passed through a
 should be defined as subclasses of the `Fw::Serializable` and define `serializeTo` and `deserializeFrom` methods to be called
 to perform the serialization.
 
+## Alias Types
+
+Alias types provide an alternate name for a type that is defined elsewhere. An alias type can refer to any type, including another alias type (excluding itself).
+
+Alias types are designed and used in the modeling of F´ and the C++ implementation is autogenerated.
+
+
 ## Conclusion
 
 F´ supports many different types, including autocoded complex types.