flatc.md Add more documentation (#8467)

* CNAME: add custom domain

* `flatc.md`: Add more documentation

docs/source/building.md

@@ -41,7 +41,7 @@ Once the project files are generated, build as normal for your platform.
 === "Unix"
 
     ```sh
-    make flatc
+    make -j
     ```
 
 === "Windows"
@@ -50,6 +50,12 @@ Once the project files are generated, build as normal for your platform.
     msbuild.exe FlatBuffers.sln
     ```
 
+=== "MacOS"
+
+    ```sh
+    xcodebuild -toolchain clang -configuration Release
+    ```
+
 ## Building with Bazel
 
 ## Building with VCPKG

docs/source/flatc.md

@@ -1,7 +1,88 @@
 # FlatBuffers Compiler (`flatc`)
 
-The main compiler for FlatBuffers is called `flatc` and is used as follows:
+The main compiler for FlatBuffers is called `flatc` and is used to convert
+schema definitions into generated code files for a variety of languages. 
+
+After [building](building.md) `flatc`, it is used as follows:
 
 ```sh
-flatc [ GENERATOR_OPTIONS ] [ -o PATH ] [- I PATH ] FILES... [ -- BINARY_FILES... ]
+flatc [ GENERATOR_OPTIONS ] [ -o PATH ] [- I PATH ] 
+  FILES... 
+  [ -- BINARY_FILES... ]
 ```
+
+* The `GENERATOR_OPTIONS` specify the language(s) to compile code for as well as
+various features to enable/disable.
+
+* The `-o PATH` specifies the path where the generated files are placed. It
+defaults to the current path if not specified.
+
+* The `-I PATH` specifies the paths where included schema files are located. It
+  defaults to the current path if not specified.
+
+## Input Files
+
+`FILES...` specifies one or more schema or data files to process. They are
+processed in the order provided.
+
+### Schema Files
+
+For schema files, language specifiers indicate what languages to generate code
+for.
+
+  * `--cpp`: C++
+  * `--java`: Java
+  * `--kotlin`: Kotlin
+  * `--csharp`: C#
+  * `--go`: Golang
+  * `--python`: Python
+  * `--js`: JavaScript
+  * `--ts`: TypeScript
+  * `--php`: PHP
+  * `--dart`: Dart
+  * `--lua`: Lua
+  * `--lobster`: Lobster
+  * `--rust`: Rust
+  * `--swift`: Swift
+  * `--nim`: Nim
+
+Additionally, adding:
+
+  * `--grpc` Will generate RPC stub code for gRPC (not available in all
+    languages)
+
+### Data Files
+
+If `FILES...` contain data files, they can be exported to either a binary or
+JSON representation.
+
+* `--binary`, `-b`: Generate a binary file containing a serialized flatbuffer.
+* `--json`, `-j`: Generate JSON file from a serialized flatbuffer.
+
+Both options require the corresponding schema file to be included first in the
+list of `FILES...`.
+
+=== "To Binary"
+
+    To serialize the JSON data in `mydata.json` using the schema `myschema.fbs`:
+
+    ```sh
+    flatc --binary myschema.fbs mydata.json
+    ```
+
+    This will generate a `mydata_wire.bin` file containing the serialized 
+    flatbuffer data.
+
+=== "To JSON"
+
+    To convert the serialized binary flatbuffer `mydata.bin` using the schema 
+    `myschema.fbs` to JSON:
+
+    ```sh
+    flatc --json myschema.fbs mydata.bin
+    ```
+
+    This will generate a `mydata.json` file.
+
+
+