Add php81-ldap for LDAP support

[thespad]

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• [x] I have read the contributing guideline and understand that I have made the correct modifications

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Description:

Closes #32

Benefits of this PR and context:

How Has This Been Tested?

Source / References:

[LinuxServer-CI]

I am a bot, here are the test results for this PR: https://ci-tests.linuxserver.io/lspipepr/grav/1.7.40-pkg-7ea8251b-pr-33/index.html https://ci-tests.linuxserver.io/lspipepr/grav/1.7.40-pkg-7ea8251b-pr-33/shellcheck-result.xml	Tag	Passed
amd64-1.7.40-pkg-7ea8251b-pr-33	✅
arm32v7-1.7.40-pkg-7ea8251b-pr-33	✅
arm64v8-1.7.40-pkg-7ea8251b-pr-33	✅