After a bit of searching I came up with 2 solutions:
solution #1:
You could just log into any linux box with ImageMagick installed, rename your source image (with a resolution of at least 256x256 pixels and a PNG format file) to 'favicon.png', and run the following command:convert favicon.png -bordercolor white -border 0 \
\( -clone 0 -resize 16x16 \) \
\( -clone 0 -resize 32x32 \) \
\( -clone 0 -resize 48x48 \) \
\( -clone 0 -resize 57x57 \) \
\( -clone 0 -resize 64x64 \) \
\( -clone 0 -resize 72x72 \) \
\( -clone 0 -resize 110x110 \) \
\( -clone 0 -resize 114x114 \) \
\( -clone 0 -resize 120x120 \) \
\( -clone 0 -resize 128x128 \) \
\( -clone 0 -resize 144x144 \) \
\( -clone 0 -resize 152x152 \) \
-delete 0 -alpha off -colors 256 favicon.ico
.. and you'll have your favicon.ico with most well-known formats baked right into one file.
Be sure to checkout the favicon cheat sheet @ https://github.com/audreyr/favicon-cheat-sheet for more favicon information.
solution #2:
At the risk of promoting a site which will eventually turns into a paid service:For those of you without Imagemagick or no knowledge on how to implement these favicons, have a look at this tip I got about https://realfavicongenerator.net/ .. it also generates HTML code and gives you a couple of extra options on how to render the file for certain platforms.