docs: copy the section of format spec to README

Author: iseki0

README.md

@@ -9,8 +9,9 @@ Reference: [https://www.bittorrent.org/beps/bep_0003.html](https://www.bittorren
 ## Usage
 
 Add the dependency to your `build.gradle.kts`
+
 ```kotlin
-dependencies{
+dependencies {
     implementation("space.iseki.bencoding:kotlinx-serialization-bencoding:0.1.+")
 }
 ```
@@ -24,3 +25,20 @@ fun foo(input: InputStream) {
 }
 ```
 
+## Bencoding Format
+
+The following content is copied
+from [https://www.bittorrent.org/beps/bep_0003.html](https://www.bittorrent.org/beps/bep_0003.html) for a memo.
+
+- Strings are length-prefixed base ten followed by a colon and the string. For example `4:spam` corresponds to 'spam'.
+- Integers are represented by an 'i' followed by the number in base 10 followed by an 'e'. For example `i3e` corresponds
+  to 3 and `i-3e` corresponds to -3. Integers have no size limitation. `i-0e` is invalid. All encodings with a leading
+  zero,
+  such as `i03e`, are invalid, other than i0e, which of course corresponds to 0.
+- Lists are encoded as an 'l' followed by their elements (also bencoded) followed by an 'e'. For
+  example `l4:spam4:eggse`
+  corresponds to ['spam', 'eggs'].
+- Dictionaries are encoded as a 'd' followed by a list of alternating keys and their corresponding values followed by
+  an 'e'. For example, `d3:cow3:moo4:spam4:eggse` corresponds to {'cow': 'moo', 'spam': 'eggs'} and `d4:spaml1:a1:bee`
+  corresponds to {'spam': ['a', 'b']}. Keys must be strings and appear in sorted order (sorted as raw strings, not
+  alphanumerics).