[DOCS] : update broken relative links between various document translations and embedded images

[pietrygamat]

Description

Several minor fixes in the included docs I have spotted when reviewing #2365

• Relative links between documents are fixed. The links in headers of all docs contain correct links to all other translations that work both in Github UI as well as in local IDE
• Headers with links are now spread into separate lines. That does not affect rendering of MD files, but should help in diffing and copy pasting when extending the language set
• Added headers with links to some languages that were missing them previously
• Fixed several broken links to images
• Minor grammar and markdown fixes in Polish readme

Contribution Checklist:

• The pull request only addresses one issue or adds one feature.
• The pull request does not introduce any breaking changes
• I have read the contribution guidelines.

[helloanoop]

Merged. Thanks for taking care of this @pietrygamat !