clipboard: Make the clipboard service work under the new service sys

This also adds a [.editorconfig](https://editorconfig.org/) and adds
apidoc.md to the gitignore.

.editorconfig

@@ -0,0 +1,5 @@
+root = true
+
+[*.lua]
+indent_style = space
+indent_size = 1

.gitignore

@@ -1,4 +1,5 @@
 *.cpio
 *.af
+apidoc.md
 /target
 /doc

service/clipboard.lua

@@ -1,11 +1,17 @@
-local lc = computer.uptime()
 _G.clip = ""
+
+function start()
+ return os.spawn(function()
+   local lc
    while true do
     local eT = {coroutine.yield()}
     if eT[1] == "clipboard" then
      if computer.uptime() > lc + 5 then
       _G.clip = ""
      end
+     lc = computer.uptime()
      _G.clip = _G.clip .. eT[3]
     end
    end
+ end)
+end