feature: add barcode extension

[jeromeag]

Add barcode feature as described here:
https://docs.asciidoctor.org/diagram-extension/latest/diagram_types/barcode/

[dduportal]

Hi @jeromeag , many thanks for this feature. It looks good and legit!

Before approving it, there are a few steps left:

• Could you give us a size (approximatively) difference before and after the change (to evaluate the change impact)?
• Could you update your change to use fixed version to the 3 new Gems (following other examples) so it would be documented by the automation, and I could add the version tracking with updatecli?

[jeromeag]

Hi @dduportal,
Thank you for your quick feedback !

Hi @jeromeag , many thanks for this feature. It looks good and legit!

Before approving it, there are a few steps left:

* Could you give us a size (approximatively) difference before and after the change (to evaluate the change impact)?

Here is the before/after results of command docker image ls after make build-load

Before:

$ docker image ls 
REPOSITORY    TAG       IMAGE ID       CREATED       SIZE
asciidoctor   latest    2de7ba181c26   4 hours ago   791MB
<none>        <none>    95010f29fbfd   4 days ago    47MB
<none>        <none>    794e485ffc6e   3 weeks ago   325MB

After:

REPOSITORY    TAG       IMAGE ID       CREATED          SIZE
asciidoctor   latest    c478415b410d   28 seconds ago   793MB
<none>        <none>    2de7ba181c26   4 hours ago      791MB
<none>        <none>    95010f29fbfd   4 days ago       47MB
<none>        <none>    794e485ffc6e   3 weeks ago      325MB

* Could you update your change to use fixed version to the 3 new Gems (following other examples) so it would be documented by the automation, and I could add the version tracking with `updatecli`?

Done !

[dduportal]

Nice job, thanks!

• I'm approving this PR and setting up to auto-merge (merging only if checks are passing but the code looks good!)
• This change only adds 2 Mb to the image: it's fine (image size is close to ~390 Mb).
• Once merged, a new release of the asciidoctor Docker image will be done to provide this change (and the gnuplot one) through a versioned release
• Subsequent PR will be created (I'll take care of it unless you are interested to do it of course) to add version tracking automation (so further Gem updates on these 3 news will end with an automated bump PR ala Dependanbot)