update README

README.md

@@ -3,11 +3,55 @@
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+`seqs` is what is commonly referred to as a userspace IP implementation. It handles:
+* Ethernet protocol
+* IP packet marshalling to sub-protocols:
+    * ARP requests and responses
+    * UDP packet handling
+    * DHCP client requests and DHCP server
+    * TCP connections over IP with support for multiple listeners on same port. These implement [net.Conn](https://pkg.go.dev/net#Conn) and [net.Listener](https://pkg.go.dev/net#Listener) interfaces. See [`stacks/tcpconn.go`](./stacks/tcpconn.go)
+
+
+### Example of use
+
+```go
+stack := stacks.NewPortStack(stacks.PortStackConfig{
+    MAC:             MAC,
+    MaxOpenPortsTCP: 1,
+    MaxOpenPortsUDP: 1,
+    MTU:             2048,
+})
+// Static IP setting.
+ip := netip.AddrFrom4([4]byte{192, 168, 1, 45}) 
+stack.SetAddr(ip)
+
+// Or can request an address via DHCP.
+dhcpClient := stacks.NewDHCPClient(stack, dhcp.DefaultClientPort)
+err = dhcpClient.BeginRequest(stacks.DHCPRequestConfig{
+    RequestedAddr: netip.AddrFrom4([4]byte{192, 168, 1, 69}),
+    Xid:           0x12345678,
+    Hostname:      "tinygo-pico",
+})
+
+for !dhcpClient.Done() {
+    time.Sleep(time.Second / 2)
+}
+
+offeredIP := dhcpClient.Offer()
+fmt.Println("got offer:", offeredIP)
+stack.SetAddr(offeredIP)
+```
+
 How to use `seqs`
 ```sh
 go mod download github.com/soypat/seqs@latest
 ```
 
+
+#### History - Precursors to seqs
+Before `seqs` there was:
+
+* [`ether-swtch`](https://github.com/soypat/ether-swtch) - First known instance of a (barely) working TCP/IP stack in Go working on embedded systems, circa June 2021. Could blink an Arduino UNO's LED via HTTP (!). Famously bad design, code, performance, readability.
+* [`dgrams`](https://github.com/soypat/dgrams) - Library prepared for Pico W's wifi chip. Already shows similarities with `seqs`. Circa May 2023.