Give alt text to Bevy logo

[BD103]

Objective

• In the documentation of the bevy crate, we embed the Bevy logo. (docs.rs, logo)
• It was first added in 9aae341.
• Markdown supports adding alternate descriptions for images that either cannot be loaded or for screen readers.

Solution

• Add alt text for the Bevy logo.

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Changelog

• Added alt text to Bevy logo.

[BD103]

I'm unsure whether this gets the A-Cross-Cutting or A-Core labels, so 🤷‍♂️.

I think the only downside to this change is that now, if the logo ever fails to load, there will be some text in its place instead of it just being empty.

This could affect the shortened docs if the bevy crate is ever re-exported. I need to test this.

[BD103]

This could affect the shortened docs if the bevy crate is ever re-exported. I need to test this.

rustdoc just ends up not giving pub use bevy; a short description in the generated output. I think this is because there is an image tag as the very first line, and unrelated to my change.

[TimJentzsch]

Yay for accessibility!