add SCRIPING.md in Markdown format and fix typo

SCRIPTING.md

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+# Overview
+
+wrk supports executing a LuaJIT script during three distinct phases: setup, running, and done. Each wrk thread has an independent scripting environment and the setup & done phases execute in a separate environment which does not participate in the running phase.
+
+The public Lua API consists of a global table and a number of global functions:
+
+```lua
+wrk = {
+    scheme  = "http",
+    host    = "localhost",
+    port    = nil,
+    method  = "GET",
+    path    = "/",
+    headers = {},
+    body    = nil,
+    thread  = <userdata>,
+}
+```
+
+```lua
+function wrk.format(method, path, headers, body)
+```
+`wrk.format` returns a HTTP request string containing the passed parameters merged with values from the wrk table.
+
+
+```lua
+function wrk.lookup(host, service)
+```
+wrk.lookup returns a table containing all known addresses for the host and service pair. This corresponds to the POSIX getaddrinfo() function.
+
+```lua
+function wrk.connect(addr)
+```
+`wrk.connect` returns `true` if the address can be connected to, otherwise
+it returns `false`. The address must be one returned from `wrk.lookup()`.
+
+The following globals are optional, and if defined must be functions:
+```
+global setup    -- called during thread setup
+global init     -- called when the thread is starting
+global delay    -- called to get the request delay
+global request  -- called to generate the HTTP request
+global response -- called with HTTP response data
+global done     -- called with results of run
+```
+
+## Setup
+
+```lua
+function setup(thread)
+```
+The setup phase begins after the target IP address has been resolved and all threads have been initialized but not yet started.
+
+`setup()` is called once for each thread and receives a userdata object representing the thread.
+
+```
+thread.addr             - get or set the thread's server address
+thread:get(name)        - get the value of a global in the thread's env
+thread:set(name, value) - set the value of a global in the thread's env
+thread:stop()           - stop the thread
+```
+
+Only boolean, `nil`, number, and string values or tables of the same may be transferred via `get()`/`set()` and `thread:stop()` can only be called while the thread is running.
+
+## Running
+
+```lua
+function init(args)
+function delay()
+function request()
+function response(status, headers, body)
+```
+
+The running phase begins with a single call to `init()`, followed by a call to `request()` and `response()` for each request cycle.
+
+The `init()` function receives any extra command line arguments for the script which must be separated from wrk arguments with "`--`".
+
+`delay()` returns the number of milliseconds to delay sending the next request.
+
+`request()` returns a string containing the HTTP request. Building a new request each time is expensive, when testing a high performance server one solution is to pre-generate all requests in `init()` and do a quick lookup in `request()`.
+
+`response()` is called with the HTTP response status, headers, and body. Parsing the headers and body is expensive, so if the response global is `nil` after the call to `init()` wrk will ignore the headers and body.
+
+## Done
+
+```lua
+function done(summary, latency, requests)
+```
+
+The `done()` function receives a table containing result data, and two statistics objects representing the per-request latency and per-thread request rate. Duration and latency are microsecond values and rate is measured in requests per second.
+
+```lua
+latency.min              -- minimum value seen
+latency.max              -- maximum value seen
+latency.mean             -- average value seen
+latency.stdev            -- standard deviation
+latency:percentile(99.0) -- 99th percentile value
+latency(i)               -- raw value and count
+```
+
+```lua
+summary = {
+    duration = N,  -- run duration in microseconds
+    requests = N,  -- total completed requests
+    bytes    = N,  -- total bytes received
+    errors   = {
+        connect = N, -- total socket connection errors
+        read    = N, -- total socket read errors
+        write   = N, -- total socket write errors
+        status  = N, -- total HTTP status codes > 399
+        timeout = N  -- total request timeouts
+    }
+}
+```