Add usage examples to README

Author: dktapps

README.md

@@ -2,3 +2,102 @@
 ![CI](https://github.com/pmmp/NBT/workflows/CI/badge.svg)
 
 PHP library for working with the NBT (Named Binary Tag) data storage format, as designed by Mojang.
+
+## Examples
+
+The library provides two NBT serializers: `BigEndianNbtSerializer` (typically suited for Minecraft Java) and `LittleEndianNbtSerializer` (typically used by Bedrock for storage).
+
+Note: Bedrock network NBT (which uses varints in some places) is not implemented here. See [BedrockProtocol](https://github.com/pmmp/BedrockProtocol) for that.
+
+Note: `TAG_LongArray` is not supported because Bedrock doesn't support it, so it's not clear how NBT trees intended for serialization by Bedrock would be restricted from using it.
+
+### Reading data
+```php
+use pocketmine\nbt\LittleEndianNbtSerializer;
+use pocketmine\nbt\NbtDataException;
+use pocketmine\nbt\NoSuchTagException;
+use pocketmine\nbt\UnexpectedTagTypeException;
+use pocketmine\nbt\tag\StringTag;
+
+$serializer = new LittleEndianNbtSerializer();
+$optionalStartOffset = 0;
+$optionalMaxDepth = 0; //unlimited by default
+$treeRoot = $serializer->read($yourInputBytes, $optionalStartOffset, $optionalMaxDepth);
+
+try{
+    //If you expect a TAG_Compound root (the most common case)
+    $data = $treeRoot->mustGetCompoundTag());
+}catch(NbtDataException $e){
+    var_dump("root isn't a TAG_Compound");
+}
+//For other, less common cases where the root tag isn't a compound
+var_dump($treeRoot->getTag());
+
+var_dump($treeRoot->getName()); //typically empty
+
+try{
+    var_dump($data->getString("hello"));
+}catch(UnexpectedTagTypeException $e){
+    var_dump("not a TAG_String");
+}catch(NoSuchTagException $e){
+    var_dump("no such tag called \"hello\"");
+}
+
+try{
+    $nestedCompound = $data->getCompoundTag("nestedCompound");
+}catch(UnexpectedTagTypeException $e){
+    var_dump("not a TAG_Compound");
+}
+if($nestedCompound === null){
+    //For legacy BC reasons, this works differently than the primitive type getters like getString() getInt() etc
+    var_dump("no such nested tag called \"nestedCompound\"");
+}
+
+try{
+    $nestedList = $data->getListTag("listOfStrings", StringTag::class);
+}catch(UnexpectedTagTypeException $e){
+    var_dump("not a list of strings");
+}
+if($nestedList === null){
+    //For legacy BC reasons, getListTag() returns NULL if the tag doesn't exist
+    var_dump("no such nested tag called \"listOfStrings\"");
+}
+var_dump($nestedList->getValue()); //StringTag[]
+```
+
+### Writing data
+
+```php
+use pocketmine\nbt\LittleEndianNbtSerializer;
+use pocketmine\nbt\TreeRoot;
+use pocketmine\nbt\tag\CompoundTag;
+use pocketmine\nbt\tag\IntTag;
+use pocketmine\nbt\tag\ListTag;
+use pocketmine\nbt\tag\StringTag;
+
+$compound = CompoundTag::create()
+    ->setByte("byte", 1)
+    ->setInt("int", 2)
+    ->setTag("list", new ListTag([
+        new StringTag("item1"),
+        new StringTag("item2")
+    ]))
+    ->setTag("compound", CompoundTag::create()
+        ->setByte("nestedByte", 1)
+    );
+
+//empty lists infer their type from the first value added
+$list = new ListTag();
+$list->push(new StringTag("hello")); //list is now ListTag<StringTag>
+try{
+    $list->push(new IntTag(1));
+}catch(\TypeError $e){
+    var_dump("can't push an int into a string list");
+}
+
+$serializer = new LittleEndianNbtSerializer();
+$bytes = $serializer->write($treeRoot);
+
+//or if you have a Tag instance
+$bytes = $serializer->write(new TreeRoot($data, "optionalRootName"));
+```