Optimize PNG files

[dilyanpalauzov]

by calling for i in $(find -name '*.png'); do optipng -o7 -zm9 $i; done.

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	❌
Fixed issues

[what-the-diff]

• The binary files of the images in docs/guide-es and docs/guide-fr were changed.
• In addition, a new image was added to guide-id folder: start-gii.png
• The binary files of the images in docs/guide-id,docs/guide-ja and docs/guide-pl were changed.
• In addition to that, some other changes are made for these languages:
  • application structure image is added into guide pl;
  • gii entry image is added into guide pt_BR;
• The binary files of the images in docs/guide-pt-BR,docs/guide-ru and docs/guide-uk are changed.
• The binary file of image application structure is changed in guide vi
• Change the language of some files from English to Vietnamese.
• Delete all images in docs/guide-vi and replace them with new ones (the same as those in docs/guide).
• Delete all images in docs/guide-zh-CN and replace them with new ones (the same as those in docs/guide).
• The binary files of versions-branches.png in docs/internals, docs/internals-ja and
  docs/internals-pl were changed.
• The binary file of exception_hierarchy.png in the same directories was also changed

[Arhell]

previously after viewing the optimized images did not notice the loss of quality
@samdark