Adds documentation for the type module

docs/type.md

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+
+# Types
+The types module can be used directly to validate records, function arguments, lists, single values, etc.
+
+You can import it as
+```javascript
+import T, { validateRecord } from 'enum-fp/types';
+```
+
+The Type module exposes the following -
+
+* [T](#type-sum-type)
+* [isOfType](#isOfType)
+* [validateRecord](#validateRecord)
+
+
+## Type sum-type
+```haskell
+data T = Any | String | Number | Bool | Record (Object T) | Map T | List T? | Enum EnumType | OneOf [T];
+```
+
+You can check if a value is of a particular type by using the isOfType function (Refer to section below for more info about isOfType)
+
+```javascript
+const isString = isOfType(T.String());
+
+isString('Hello world') // > true
+isString(1) // > false
+```
+
+## isOfType
+```haskell
+isOfType :: T -> a -> Boolean
+```
+
+You can use this function to write helper functions for validating types
+
+```javascript
+const isString = isOfType(T.String());
+const isNumber = isOfType(T.Number());
+
+const isUser = isOfType(T.Record({
+    name: T.String(),
+    age: T.Number(),
+}));
+
+isUser({ name: 'Akshay Nair', age: 21 }); // > true
+isUser({ name: 'Akshay Nair', age: '21' }); // > false
+isUser({ name: 'Akshay Nair' }); // > false
+```
+
+
+## validateRecord
+```haskell
+validateRecord :: (Object T, a) -> Boolean
+```
+
+Validates if the passed object is of the specified shape. The check is strict so missing fields in an object means the object is invalid. (Kind of an alternate api for `isOfType(T.Record({ /* shape */ }))`)
+
+Here's the above isOfType example for user
+```javascript
+const isUser = user => validateRecord({
+    name: T.String(),
+    age: T.Number(),
+}, user);
+```