feat(docs): update readme, added license

Signed-off-by: MastahSenpai <26342994+ii64@users.noreply.github.com>

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2021 Ii64人
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -1,7 +1,79 @@
 # gouring
 
-Low-lavel io uring library
+
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](LICENSE)
+[![Go Reference](https://pkg.go.dev/badge/github.com/ii64/gouring.svg)](https://pkg.go.dev/github.com/ii64/gouring)
+
+Low-level io uring library
 
 ```
 go get github.com/ii64/gouring
-```
+```
+
+## Example
+
+```go
+import "github.com/ii64/gouring"
+import "github.com/ii64/gouring/queue"
+
+// io_uring_setup
+ring, err := gouring.New(256, nil) // default io uring setup param
+if err != nil {
+    // ...
+}
+defer ring.Close() // munmap shared memory, cleanup
+var (
+    ret int
+    err error
+)
+
+// io_uring_register
+ret, err = ring.Register(gouring.IORING_REGISTER_BUFFERS, addr, nrArg)
+
+// io_uring_enter
+ret, err = ring.Enter(toSubmit, minComplete, gouring.IORING_ENTER_GETEVENTS, nil)
+
+// setup param
+params := ring.Params()
+
+// ring fd
+fd := ring.Fd()
+
+// Submission Queue
+sq := ring.SQ()
+
+// Completion Queue
+cq := ring.CQ()
+
+/* Using queue package */
+q := queue.New(ring)
+go func() {
+    q.Run(func(cqe *gouring.CQEntry) {
+        // cqe processing
+        _ = cqe.UserData
+        _ = cqe.Res
+        _ = cqe.Flags
+    })
+}()
+
+// buffer
+data := []byte("print on stdout\n")
+
+// get sqe
+sqe := q.GetSQEntry()
+sqe.UserData = 0 // identifier / event id
+sqe.Opcode = gouring.IORING_OP_WRITE // op write
+sqe.Fd = int32(syscall.Stdout) // fd 1
+sqe.Len = uint32(len(data)) // buffer size
+sqe.SetOffset(0) // fd offset
+sqe.SetAddr(&data[0]) // buffer addr
+
+// submit sqe
+submitted, err := q.Submit()
+if err != nil {
+    // ...
+}
+```
+
+### Referece
+[github.com/iceber/iouring-go](https://github.com/iceber/iouring-go)