Update circle flags

[kapowaz]

[Supersedes #108. I’ve created a new PR based on a specific branch, since I unintentionally used main previously. This will let me continue to make other changes to my fork without them appearing in the PR to the base repo. Apologies for the noise!]

This might be a controversial PR, but I thought it was worth sharing!

You may be already aware I have created the square-flags project derived from the original circle-flags icons. There are lots of small improvements I’ve made, initially to cater for the square format, but as I made more and more changes I saw opportunities to improve other things besides:

• Use the navy colour for flags that are more obviously navy than royal blue (e.g. Australia)
• Add a darker yellow that has better contrast with lighter shades, and updated various elements to use it
• Improved alignment with the pixel grid for various stripes and crosses etc.
• Improved alignment of details in corners of flags (e.g. Georgia) so as to work better with a square background
• Fixed smaller details on some flags that seemed overly minimalist (e.g. India, Iran)

All of this can continue to exist as its own project, but since I created it as a Figma project I was able to take the work and apply a number of these changes back on the circular format. That’s what this PR is all about.

I’ve created an image which shows the difference between the existing flags and the updated versions in this PR, but you can also see the diff per-flag within the PR: