[coro_rpc] fix document (#246)

src/coro_rpc/doc/coro_rpc_introduction_cn.md

@@ -64,7 +64,7 @@ client调用rpc函数也同样简单，5，6行代码就可以实现rpc调用了
 
 相信上面的这个简单的例子已经充分展示了coro_rpc的易用性和特点了，也体现了rpc的本质，即用户可以像调用本地函数那样调用远程函数，用户只需要关注rpc函数的业务逻辑即可。
 
-coro_rpc的接口易用性还体现在rpc函数几乎没有任何限制，你可以定义任意个数和任意类型参数的rpc函数, 参数的序列化和反序列化由rpc库自动完成，用户无需关心。
+coro_rpc的接口易用性还体现在rpc函数几乎没有任何限制，rpc函数可以拥有任意多个参数，参数的序列化和反序列化由rpc库自动完成，用户无需关心。rpc库支持的参数类型相当广泛详见：[struct_pack的类型系统](https://alibaba.github.io/yalantinglibs/zh/guide/struct-pack-type-system.html)
 
 ## rpc函数支持任意参数
 
@@ -391,4 +391,4 @@ OS: Linux version 4.9.151-015.ali3000.alios7.x86_64
 
 1. 目前只支持小端，兼容大端的工作正在做；
 2. 目前只支持C++，暂时还不支持跨语言；编译器要求能支持C++20(clang13, gcc10.2,  msvc2022)；
-3. gcc如果在O3下出现链接失败，请开启选项-fno-tree-slp-vectorize以禁用该优化选项。
+3. gcc如果在O3下出现链接失败，请开启选项-fno-tree-slp-vectorize以禁用该优化选项。

src/coro_rpc/doc/coro_rpc_introduction_en.md

@@ -52,7 +52,7 @@ As demonstrated above, it is also very convenient to build a client. There's not
 
 The server/client implementation shows the usability and core features of coro_rpc. Also, it shows us the core concept of RPC: that users can invoke remote methods in a way with local functions, and users will focus their efforts on RPC functions.
 
-Another usability of coro_rpc is that: there are barely any constraints on the RPC function itself. One could define an RPC function with any number of parameters of any type. The serialization/deserialization procedures are transparent to users and the RPC framework will take care of them automatically.
+Another usability of coro_rpc is that: there are barely any constraints on the RPC function itself. One could define an RPC function with any number of parameters. The parameters' type should be legal for struct_pack. (See [struct pack type system](https://alibaba.github.io/yalantinglibs/guide/struct-pack-type-system.html)). The serialization/deserialization procedures are transparent to users and the RPC framework will take care of them automatically.
 
 ## RPC with any parameters