I use [Static Site Generator | Nikola](https://getnikola.com/). Each post has  a header like as follows:

    <!--
    .. title: Some interesting title
    .. slug: some-interesting-title
    .. date: 2017-01-25 06:32:15 UTC-03:00
    .. tags: tag1,tag2
    .. category: Enlaces
    .. link:
    .. description: bla, bla, bla
    .. type: text
    -->

My idea is create a file with tags (tag1, tag2, ... tagn), and to use  insert mode completion, whith CTRL-X and CTRL-I.
But I have no idea about how to set an included file in order to vim find in it.

Edited:

I've found in the documentation:

    CTRL-X CTRL-I		Search for the first keyword in the current and
    			included files that starts with the same characters
    			as those before the cursor.  The matched keyword is
    			inserted in front of the cursor.


I haven't found how and/or where declare such a files.

Any ideas?