[Core] Update README.md formatting and add emojis for better readability

[loumalouomega]

📝 Description

This PR updates the README.md file for the Kratos Multiphysics project. The changes include the addition of emojis to various headings to improve readability and make the content more visually appealing. Section headings have also been converted to use proper Markdown hierarchy, improving the document's overall structure. No changes have been made to the actual content or meaning of the text.

🆕 Changelog

• Update README.md

[matekelemen]

I´m fine with memes and emojis in the source code, but I can´t say I´m thrilled about putting them in the docs, especially in the main readme.

[loumalouomega]

I´m fine with memes and emojis in the source code, but I can´t say I´m thrilled about putting them in the docs, especially in the main readme.

Everyone does that :P

[loumalouomega]

I´m fine with memes and emojis in the source code, but I can´t say I´m thrilled about putting them in the docs, especially in the main readme.

We can add some, but not all of them

[loumalouomega]

I guess I should close this?

[rubenzorrilla]

Just saying that I'm fine with the changes.

[RiccardoRossi]

well, to be honest i share @matekelemen 's opinion on this. Do we really want the emoticons in the readme??

[loumalouomega]

well, to be honest i share @matekelemen 's opinion on this. Do we really want the emoticons in the readme??

UwU (okay I remove them)

[RiccardoRossi]

waitwait, let's see what other think about

[loumalouomega]

waitwait, let's see what other think about

I left one