[SEO] Fix issues for blog/ and blog/…

[mebjas]

Page speed insights: https://pagespeed.web.dev/report?url=https%3A%2F%2Fscanapp.org%2Fblog&hl=en&form_factor=mobile

[mebjas]

After latest fixes

#	Performance	Accessibility	best practices	SEO
Mobile	99	100	100	100
Desktop	100	100	100	100

Happy with the results!

Pending action items:

1. Image elements do not have explicit width and height : need to find a way to do this for mobile and desktop together. - https://web.dev/optimize-cls/?utm_source=lighthouse&utm_medium=lr#images-without-dimensions
2. A long cache lifetime can speed up repeat visits to your page. Learn more. --> to be done together with [Performance] Setup large TTL caching for static contents #24

[mebjas]

Some additional tool references:

• https://tools.pingdom.com/#61ac3b4d72800000
• https://www.debugbear.com/project/32521?group=recentlyAdded&nNewPages=2