Add new Docs source files (#8461)

docs/source/index.md

@@ -0,0 +1,59 @@
+# Overview
+
+FlatBuffers is an efficient cross platform serialization library for C++, C#, C,
+Go, Java, Kotlin, JavaScript, Lobster, Lua, TypeScript, PHP, Python, Rust and
+Swift. It was originally created at Google for game development and other
+performance-critical applications.
+
+It is available as Open Source on
+[GitHub](https://github.com/google/flatbuffers) under the Apache license v2.0.
+
+## Why Use FlatBuffers?
+
+<div class="grid cards" markdown>
+
+- :material-clock-fast:{ .lg .middle } **Access to serialized data without
+  parsing/unpacking**
+
+    ---
+    Access the data directly without unpacking or parsing.
+
+- :material-memory:{ .lg .middle } **Memory Efficiency and Speed**
+
+    ---
+    The only memory needed to access your data is that of the buffer. No heap is
+  required.
+
+- :material-compare-horizontal:{ .lg .middle } **Backwards and Forwards
+  Compatibility**
+
+    ---
+    The only memory needed to access your data is that of the buffer. No heap is
+  required.
+
+- :material-scale-off:{ .lg .middle } **Small Footprint**
+
+    ---
+    Minimal dependencies and small code footprint.
+
+</div>
+
+## Why not use...
+
+=== "Protocol Buffers"
+
+    Protocol Buffers is indeed relatively similar to FlatBuffers, with the primary
+    difference being that FlatBuffers does not need a parsing/unpacking step to a
+    secondary representation before you can access data, often coupled with
+    per-object memory allocation. The code is an order of magnitude bigger, too.
+
+=== "JSON"
+
+    JSON is very readable (which is why we use it as our optional text format) and
+    very convenient when used together with dynamically typed languages (such as
+    JavaScript). When serializing data from statically typed languages, however,
+    JSON not only has the obvious drawback of runtime inefficiency, but also forces
+    you to write more code to access data (counterintuitively) due to its
+    dynamic-typing serialization system. In this context, it is only a better choice
+    for systems that have very little to no information ahead of time about what
+    data needs to be stored.