astro 2.0.15

#6323 5e26bc891 Thanks @Princesseuh! - Updated Undici to 5.20.0. This fixes a security issue and handling of cookies in certain cases in dev
#6293 a156ecbb7 Thanks @MoustaphaDev! - Warn about setting the allowJs compiler option only when the content directory exists.
#6320 ccd72e6bb Thanks @wulinsheng123! - fix #6020
#6347 504c7bacb Thanks @natemoo-re! - Fix internal getSetCookie usage for undici@5.20.x
#6333 63dda6ded Thanks @ematipico! - Correctly emit mode when passing node to the command astro add
#6330 f91a7f376 Thanks @MoustaphaDev! - Ensure prefixed underscore ignores only child paths of the content directory.