#793 Add ESCET icon to ESCET IDE launchers for Linux and macOS

Regarding the XPM file for Linux:

• I created one using ImageMagick: magick convert eclipse-escet-icon-256x256.png eclipse-escet-icon.xpm
• Note that XPM does not support partial transparency, so either a pixel is non-transparent or fully transparent.
• Note that XPM does not support multiple resolutions, so I used the 256x256 pixels one, as the Eclipse IDE also does.
• Read more about the file format at https://en.wikipedia.org/wiki/X_PixMap.
• I added it to the misc/escet-logo folder, and to the product.
• I excluded .xpm from the license header check.

Regarding the ICNS file for macOS:

• I have added 512x512 pixels and 1024x1024 pixels versions of the ESCET icon.
• I have not yet created the .icns file, but one can be created, from the branch of this merge request, by executing the following in the misc/escet-logo folder, on macOS:

  mkdir tmp-icons
  cp eclipse-escet-icon-16x16.png tmp-icons/icon_16x16.png
  cp eclipse-escet-icon-32x32.png tmp-icons/icon_16x16@2.png
  cp eclipse-escet-icon-32x32.png tmp-icons/icon_32x32.png
  cp eclipse-escet-icon-64x64.png tmp-icons/icon_32x32@2.png
  cp eclipse-escet-icon-64x64.png tmp-icons/icon_64x64.png
  cp eclipse-escet-icon-128x128.png tmp-icons/icon_64x64@2.png
  cp eclipse-escet-icon-128x128.png tmp-icons/icon_128x128.png
  cp eclipse-escet-icon-256x256.png tmp-icons/icon_128x128@2.png
  cp eclipse-escet-icon-256x256.png tmp-icons/icon_256x256.png
  cp eclipse-escet-icon-512x512.png tmp-icons/icon_256x256@2.png
  cp eclipse-escet-icon-512x512.png tmp-icons/icon_512x512.png
  cp eclipse-escet-icon-1024x1024.png tmp-icons/icon_512x512@2.png
  iconutil --convert icns -o eclipse-escet-icon.icns tmp-icons

• This merge request is a draft until I get the .icns file to also include.
• I have already added .icns as a binary file extension to .gitattributes.
• I excluded .icns from the license header check. I saw that .pptx is in the wrong category, so I moved that as well.

Closes #793 (closed)