docs(timeutil): generate API docs (#7)

Co-authored-by: haithium <128622475+haithium@users.noreply.github.com>

Author: github-actions[bot]

docs/src/timeutil/timeutil.md

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+---
+description: "Wall-clock time, monotonic time, and native sleep utilities."
+---
+
+# `timeutil`
+
+Wall-clock time, monotonic time, and native sleep utilities.
+
+```lua
+local timeutil = require("timeutil")
+local start = timeutil.mono()
+timeutil.sleep(0.1)
+print(timeutil.now() - start)
+```
+
+## Functions
+
+<a id="fn-mono"></a>
+
+### `mono()`
+
+Returns monotonic elapsed time in seconds.
+
+**Return**:
+
+- `seconds` (`number`)
+
+**Example**:
+
+```lua
+local time = require("timeutil")
+local monotime = time.mono
+
+local start = monotime()
+time.sleep(0.5)
+local stop = monotime()
+
+local elapsed_ms = math.floor((stop - start) * 1000)
+print(elapsed_ms.."ms") --> 500ms
+```
+
+<a id="fn-now"></a>
+
+### `now()`
+
+Returns wall-clock Unix time in seconds.
+
+**Return**:
+
+- `seconds` (`number`)
+
+**Example**:
+
+```lua
+local time = require("timeutil")
+local now = time.now()
+local seconds = math.floor(now)
+local ms = math.floor((now - seconds) * 1000)
+local dt = string.format("%s.%03d", os.date("%Y-%m-%d %H:%M:%S", seconds), ms)
+print(dt) --> YYYY-MM-DD HH:mm:ss.SSS
+```
+
+<a id="fn-sleep"></a>
+
+### `sleep(seconds)`
+
+Blocks the current thread for the requested non-negative duration.
+
+**Parameters**:
+
+- `seconds` (`number`)
+
+**Example**:
+
+```lua
+local time = require("timeutil")
+time.sleep(1.5) -- sleep for 1.5 seconds
+```