docs: add basic usage guide

Author: MunifTanjim

README.md

@@ -2,6 +2,96 @@
 
 LuaJIT FFI Bindings for [`libevdev`](https://gitlab.freedesktop.org/libevdev/libevdev).
 
+## Usage
+
+### Initializing a Device
+
+```lua
+local Device = require("evdev.device")
+
+---@param dev Device
+local function print_device(dev)
+  local name = dev:name():gsub("\n", " | ")
+  print("============", "===")
+  print("= Pathname: ", dev.pathname)
+  print("=     Name: ", name)
+  print("=     Phys: ", dev:phys())
+  print("=     Uniq: ", dev:uniq())
+  print("=  Product: ", dev:id_product())
+  print("=   Vendor: ", dev:id_vendor())
+  print("=  Bustype: ", dev:id_bustype())
+  print("=  Version: ", dev:id_version())
+  print("============", "===")
+end
+
+local dev = Device:new("/dev/input/event7")
+
+print_device(dev)
+```
+
+### Reading Events from a Device
+
+```lua
+local Event = require("evdev.event")
+local Device = require("evdev.device")
+local libevdev = require("evdev.libevdev")
+local input = require("evdev.linux.input")
+
+local enum = libevdev.enum
+local input_constant = input.constant
+
+---@param ev Event
+local function print_event(ev)
+  print(string.format("{'%s', '%s', %d};", ev:type_name(), ev:code_name(), ev:value()))
+end
+
+---@param dev Device
+---@param initial_state table
+local function events(dev, initial_state)
+  initial_state = initial_state or {}
+
+  if not initial_state.read_flag then
+    initial_state.read_flag = initial_state.read_flag or enum.libevdev_read_flag.NORMAL
+  end
+
+  if not initial_state.should_skip then
+    initial_state.should_skip = function()
+      return false
+    end
+  end
+
+  local function iter(state)
+    local rc, ev = 0, Event:new()
+
+    repeat
+      rc, ev = dev:next_event(state.read_flag, ev)
+      if (rc == enum.libevdev_read_status.SUCCESS) or (rc == enum.libevdev_read_status.SYNC) then
+        if not state.should_skip(ev) then
+          return ev, state
+        end
+      end
+    until rc ~= enum.libevdev_read_status.SUCCESS and rc ~= enum.libevdev_read_status.SYNC and rc ~= -11
+
+    return nil, state
+  end
+
+  return iter, initial_state
+end
+
+local dev = Device:new("/dev/input/event7")
+
+local initial_state = {
+  ---@param ev Event
+  should_skip = function(ev)
+    ev:is_type(input_constant.EV_KEY)
+  end,
+}
+
+for ev in events(dev, initial_state) do
+  print_event(ev)
+end
+```
+
 ## License
 
 Licensed under the MIT License. Check the [LICENSE](./LICENSE) file for details.