I'm using grav-skeleton-blog-site templates. Everything is going well except for one small SEO suggestion. The blog page displays recent items using blog-list-item-html-twig
This twig line: <a aria-label="link to {{ page.title }} article" href="{{ page.url }}">{{ image.cropZoom(800,400).html|raw }}</a>
creates this HTML: <a aria-label="link to Congratulations to the High School Class of 2020 article" href="/articles/congratulations-to-the-high-school-class-of-2020"><img alt="" src="/images/7/e/0/9/9/7e099ac3c7a5f83a7fd345bc6b11031f571ce79f-congratulations-to-the-class-of-2020.jpeg"></a>
@unleashed, Meta data of an image can be stored in a separate meta file, which has the same name as the image, but extended with .meta.yaml. In your case that would be congratulations-to-the-class-of-2020.jpeg.meta.yaml. This file is stored in the same folder as the image.
In that file you can add any yaml you like. For example:
YAML
title:Title of the imagealt:Alt text of image
In Twig, this meta data can be accessed using image.meta.title
The Grav method Media::html() has a few parameters among which 'title' and 'alt'
In template '/templates/partials/blog-list-item.html.twig' you can now add these parameters to the Medium::html() function.
Important note: When changing files (eg. a template) in a theme, these changes will be lost when a new release of the theme is installed. Therefor, you should make these changes in a so called inherited theme.
p.s.
FWIW, I would prefer not to create a new meta file for each article image. Instead I added alt: 'my alt text' to the page header and used the existing header title.
TWIG
<aaria-label="link to {{page.title}} article"href="{{page.url}}">{{image.cropZoom(800,400).html(page.header.title, page.header.alt)|raw}}</a>