Fix new_article.py script

[ctmbl]

The script fails to create the right URL for article's file containing Upper case letters because HUGO only generates endpoints with lower case see:

± ls -1 src/content/posts/
WU2024-Base64Custom.md
introducing-poison.md
minishell_wu_pwn.md
multiplayer_online_game.md
publish-your-own-post
reversing-alien-gibberish-xlitoni.md
short-docker-introduction.md
simple-discordpy-tutorial.md
useful-daily-linux-tools.md
web3py-solidity-write-up.md
wu_fcsc_2022_a_l_envers.md

± ls -1 build/blog/posts/
index.html
index.xml
introducing-poison
minishell_wu_pwn
multiplayer_online_game
page
publish-your-own-post
reversing-alien-gibberish-xlitoni
short-docker-introduction
simple-discordpy-tutorial
useful-daily-linux-tools
web3py-solidity-write-up
wu2024-base64custom
wu_fcsc_2022_a_l_envers

The fix is easy: lower case the url in the new_article script, it might also be a good thing to enforce guidelines when it comes to article files name:

• only lower case
• use dash - instead of underscore _ or whitespace
• special guidelines for WU

[ctmbl]

https://github.com/iScsc/blog.iscsc.fr/pull/59 fixes this

But I'll let this open to discuss about article files name guidlines

[ctmbl]

• [ ] Deal with guidelines: automatic enforcement though workflow, CONTRIBUTING.md, ...

[ctmbl]

I downgraded the priority now that #59 fixed it, but still we should deal with the guidelines subject

[ctmbl]

https://github.com/iScsc/blog.iscsc.fr/issues/65 has been open so this can be definitely close