chore(readme): add basic descriptions

README.md

-# Pier Client Fabric
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+# Pier Client Fabric
+
+Pier-client-fabric is the plugin implementation for fabric blockchain.
+
+## How to build
+
+Use the following command to build
+
+```shell script
+make fabric1.4
+```
+
+This will create a `build` directory under the project path and generate a `fabric-client-1.4.so` inside the `build`.
+This `.so` file will be used by [Pier](https://github.com/meshplus/pier).
+
+## Usage
+
+Details about how to use this plugin can be found in [here](https://github.com/meshplus/pier/wiki/Pier%E4%BD%BF%E7%94%A8%E6%96%87%E6%A1%A3)