Add end-to-end example installation script

[RidaAyed]

I struggled finding a deterministic setup example of this nice short-code gallery.
I hope this PR helps others to get a quick hand-on glimpse on using this gallery.

[mfg92]

Thank you very much for your PR. I think this is a great idea.
I reviewed the first half of the script, can you have a look at my comments and adress them? Thank you!

[iaeiou]

I gave it a try and it works, but only the first time.

To run again, I had to delete the folder /tmp/mysite

[faaafo]

@iaeiou uncomment the sudo rm.. lines b7fcc9e

[RoneoOrg]

Successfully tested too, on Debian 10 with hugo v0.80.0/extended, thanks @RidaAyed !

(It seems like the script accepts arguments, maybe it is worth adding a line about it to the Readme?)

[RoneoOrg]

The first commit brings an issue:
(it's in french but I guess you'll get it)

$ git add .

warning: dépôt git embarqué ajouté : themes/hugo-shortcode-gallery
astuce: You've added another git repository inside your current repository.
astuce: Clones of the outer repository will not contain the contents of
astuce: the embedded repository and will not know how to obtain it.
astuce: If you meant to add a submodule, use:
astuce: 
astuce: 	git submodule add <url> themes/hugo-shortcode-gallery

@RidaAyed , why do you use git clone instead of git submodule add, line 90?

Thanks again BTW, it's working great apart from this tiny issue

[RoneoOrg]

The first commit brings an issue:

Solved by replacing the lines 89 and 90 with
git submodule add https://github.com/mfg92/hugo-shortcode-gallery.git themes/hugo-shortcode-gallery

[RidaAyed]

@RoneoOrg Thank you

[RoneoOrg]

Used again today, super useful!

Tiny potential improvement: the default gallery.md is set to draft:true, and shows a 404 when rebuilding the generated site with a simple hugo serve (without BuildDraft).
That's no big deal but I needed a few minutes to figure out and others may also waste time on it.

[RidaAyed]

Can you elaborate? The script doesn't generate a file named gallery.md, but gallery/index.md and my-first-post.md. Only the latter contains draft:true

[RoneoOrg]

Can you elaborate? The script doesn't generate a file named gallery.md, but gallery/index.md and my-first-post.md. Only the latter contains draft:true

I double-checked with a fresh download of the script and gallery/index.md also contains draft:true, which prevent the page to be displayed with a basic hugo command