Fix & enhance some docs (#857)

doc/stub/global.lua

@@ -77,7 +77,7 @@ the prompt.
 @treturn string The text typed in.
 
 @see cc.completion For functions to help with completion.
-@usage Read an string and echo it back to the user
+@usage Read a string and echo it back to the user
 
     write("> ")
     local msg = read()

src/main/java/dan200/computercraft/core/apis/FSAPI.java

@@ -364,6 +364,8 @@ public final void delete( String path ) throws LuaException
      *   lines[#lines + 1] = line
      * end
      *
+     * file.close()
+     *
      * print(lines[math.random(#lines)]) -- Pick a random line and print it.
      * }</pre>
      * @cc.usage Open a file and write some text to it. You can run {@code edit out.txt} to see the written text.

src/main/java/dan200/computercraft/shared/peripheral/modem/ModemPeripheral.java

@@ -161,7 +161,7 @@ public final void closeAll()
      *
      * @param channel      The channel to send messages on.
      * @param replyChannel The channel that responses to this message should be sent on.
-     * @param payload      The object to send. This can be a string, number, or table.
+     * @param payload      The object to send. This can be a boolean, string, number, or table.
      * @throws LuaException If the channel is out of range.
      */
     @LuaFunction