Update dependency astro to v4.15.4

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
astro (source)	4.15.3 -> 4.15.4

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Release Notes

withastro/astro (astro)

v4.15.4

Compare Source

Patch Changes

• #​11879 bd1d4aa Thanks @​matthewp! - Allow passing a cryptography key via ASTRO_KEY

  For Server islands Astro creates a cryptography key in order to hash props for the islands, preventing accidental leakage of secrets.

  If you deploy to an environment with rolling updates then there could be multiple instances of your app with different keys, causing potential key mismatches.

  To fix this you can now pass the ASTRO_KEY environment variable to your build in order to reuse the same key.

  To generate a key use:

  astro create-key
  

  This will print out an environment variable to set like:

  ASTRO_KEY=PIAuyPNn2aKU/bviapEuc/nVzdzZPizKNo3OqF/5PmQ=
  

• #​11935 c58193a Thanks @​Princesseuh! - Fixes astro add not using the proper export point when adding certain adapters

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