Add EventSource example

Port from extend/cowboy_examples.

examples/eventsource/src/eventsource.app.src

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+%% Feel free to use, reuse and abuse the code in this file.
+
+{application, eventsource, [
+	{description, "Cowboy EventSource example."},
+	{vsn, "1"},
+	{modules, []},
+	{registered, []},
+	{applications, [
+		kernel,
+		stdlib,
+		cowboy
+	]},
+	{mod, {eventsource_app, []}},
+	{env, []}
+]}.

examples/eventsource/src/eventsource.erl

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+%% Feel free to use, reuse and abuse the code in this file.
+
+-module(eventsource).
+
+%% API.
+-export([start/0]).
+
+%% API.
+
+start() ->
+	ok = application:start(crypto),
+	ok = application:start(ranch),
+	ok = application:start(cowboy),
+	ok = application:start(eventsource).

examples/eventsource/src/eventsource_app.erl

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+%% Feel free to use, reuse and abuse the code in this file.
+
+%% @private
+-module(eventsource_app).
+-behaviour(application).
+
+%% API.
+-export([start/2]).
+-export([stop/1]).
+
+%% API.
+
+start(_Type, _Args) ->
+	Dispatch = cowboy_router:compile([
+		{'_', [
+			{"/eventsource", eventsource_handler, []},
+			{"/", cowboy_static, [
+				{directory, {priv_dir, eventsource, []}},
+				{file, <<"index.html">>},
+				{mimetypes, {fun mimetypes:path_to_mimes/2, default}}
+			]}
+		]}
+	]),
+	{ok, _} = cowboy:start_http(http, 100, [{port, 8080}], [
+		{env, [{dispatch, Dispatch}]}
+	]),
+	eventsource_sup:start_link().
+
+stop(_State) ->
+	ok.

examples/eventsource/src/eventsource_handler.erl

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+%% Feel free to use, reuse and abuse the code in this file.
+
+%% @doc EventSource emitter.
+-module(eventsource_handler).
+
+-export([init/3]).
+-export([info/3]).
+-export([terminate/3]).
+
+init(_Transport, Req, []) ->
+	Headers = [{<<"content-type">>, <<"text/event-stream">>}],
+	{ok, Req2} = cowboy_req:chunked_reply(200, Headers, Req),
+	erlang:send_after(1000, self(), {message, "Tick"}),
+	{loop, Req2, undefined, 5000}.
+
+info({message, Msg}, Req, State) ->
+	ok = cowboy_req:chunk(["id: ", id(), "\ndata: ", Msg, "\n\n"], Req),
+	erlang:send_after(1000, self(), {message, "Tick"}),
+	{loop, Req, State}.
+
+terminate(_Reason, _Req, _State) ->
+	ok.
+
+id() ->
+	{Mega, Sec, Micro} = erlang:now(),
+	Id = (Mega * 1000000 + Sec) * 1000000 + Micro,
+	integer_to_list(Id, 16).

examples/eventsource/src/eventsource_sup.erl

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+%% Feel free to use, reuse and abuse the code in this file.
+
+%% @private
+-module(eventsource_sup).
+-behaviour(supervisor).
+
+%% API.
+-export([start_link/0]).
+
+%% supervisor.
+-export([init/1]).
+
+%% API.
+
+-spec start_link() -> {ok, pid()}.
+start_link() ->
+	supervisor:start_link({local, ?MODULE}, ?MODULE, []).
+
+%% supervisor.
+
+init([]) ->
+	Procs = [],
+	{ok, {{one_for_one, 10, 10}, Procs}}.