doc: document object iterators (#1090)

Signed-off-by: Darshan Sen <[email protected]>

Author: RaisinTen

doc/object.md

@@ -288,6 +288,34 @@ Napi::Value Napi::Object::operator[] (uint32_t index) const;
 
 Returns an indexed property or array element as a [`Napi::Value`](value.md).
 
+### begin()
+
+```cpp
+Napi::Object::iterator Napi::Object::begin() const;
+```
+
+Returns a constant iterator to the beginning of the object.
+
+```cpp
+Napi::Object::iterator Napi::Object::begin();
+```
+
+Returns a non constant iterator to the beginning of the object.
+
+### end()
+
+```cpp
+Napi::Object::iterator Napi::Object::end() const;
+```
+
+Returns a constant iterator to the end of the object.
+
+```cpp
+Napi::Object::iterator Napi::Object::end();
+```
+
+Returns a non constant iterator to the end of the object.
+
 ## Iterator
 
 Iterators expose an `std::pair<...>`, where the `first` property is a
@@ -300,6 +328,41 @@ exceptions are enabled (by defining `NAPI_CPP_EXCEPTIONS` during the build).
 
 In constant iterators, the iterated values are immutable.
 
+#### operator++()
+
+```cpp
+inline Napi::Object::const_iterator& Napi::Object::const_iterator::operator++();
+```
+
+Moves the iterator one step forward.
+
+#### operator==
+
+```cpp
+inline bool Napi::Object::const_iterator::operator==(const Napi::Object::const_iterator& other) const;
+```
+- `[in] other`: Another iterator to compare the current iterator to.
+
+Returns whether both iterators are at the same index.
+
+#### operator!=
+
+```cpp
+inline bool Napi::Object::const_iterator::operator!=(const Napi::Object::const_iterator& other) const;
+```
+- `[in] other`: Another iterator to compare the current iterator to.
+
+Returns whether both iterators are at different indices.
+
+#### operator*()
+
+```cpp
+inline const std::pair<Napi::Value, Napi::Object::PropertyLValue<Napi::Value>> Napi::Object::const_iterator::operator*() const;
+```
+
+Returns the currently iterated key and value.
+
+#### Example
 ```cpp
 Value Sum(const CallbackInfo& info) {
   Object object = info[0].As<Object>();
@@ -317,6 +380,41 @@ Value Sum(const CallbackInfo& info) {
 
 In non constant iterators, the iterated values are mutable.
 
+#### operator++()
+
+```cpp
+inline Napi::Object::iterator& Napi::Object::iterator::operator++();
+```
+
+Moves the iterator one step forward.
+
+#### operator==
+
+```cpp
+inline bool Napi::Object::iterator::operator==(const Napi::Object::iterator& other) const;
+```
+- `[in] other`: Another iterator to compare the current iterator to.
+
+Returns whether both iterators are at the same index.
+
+#### operator!=
+
+```cpp
+inline bool Napi::Object::iterator::operator!=(const Napi::Object::iterator& other) const;
+```
+- `[in] other`: Another iterator to compare the current iterator to.
+
+Returns whether both iterators are at different indices.
+
+#### operator*()
+
+```cpp
+inline std::pair<Napi::Value, Napi::Object::PropertyLValue<Napi::Value>> Napi::Object::iterator::operator*();
+```
+
+Returns the currently iterated key and value.
+
+#### Example
 ```cpp
 void Increment(const CallbackInfo& info) {
   Env env = info.Env();