Fixed display corruption on smartphones and added a translator credit to myself in the footer section of each Japanese pages.

ref: https://github.com/quinton-ashley/p5play-web/pull/34#issuecomment-2063086625
- ```
#md15 {
height: calc(100% - 40px);
overflow-y: auto;
}
```
Shortened translation of index text "Quinton Ashley によって作成されました" into "Quinton Ashley により作成".
Suppressed unnatural line breaks in Japanese within {text-align: center} blocks.
- Added <wbr /> tags between each "Bunsetsu" (文節, lit. "Clauses in a sentence". It means phrases or chunks in the Japanese sentence) to text in the blocks in ja/index.md.
- Added style {word-break: keep-all;overflow-wrap: anywhere;} to the blocks.

Knowledges:

About styling:
- https://developer.mozilla.org/docs/Web/CSS/word-break
- https://developer.mozilla.org/docs/Web/CSS/overflow-wrap
About Bunsetsu:
- (Japanese page) https://ja.wikipedia.org/w/index.php?curid=310020
- Translated by ChatGPT:
  
  A "bunsetsu" is the smallest unit in Japanese grammar (both classical and modern Japanese grammar) that can be divided without creating unnatural breaks when words are segmented. It is also a unit pronounced without pausing in spoken language. Although there is some discrepancy between linguistic and terminological usage, it is similar to what linguists refer to as a "word."

quinton-ashley / p5play-web