update the readme to explain our design goals and principle
# README
+Orca is a discord bot framework that is designed with minimum dependencies to
+make bot deployment dead simple. The primary design goals of this framework are:
+
+- easy to debug (networking and logic) errors with extensive logging facilities
+- easy to reason about the code
+- easy to use for the end users: asynchrous programming model is hard to reasonable.
+ Our lib uses multi-threading and synchronous IO to support concurrency.
+
## Build
### Install dependencies:
- gcc, make
