Add user-installation + DNSSEC disabling to DNS over Discord

[MattIPv4]

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Summary

Update docs to match the upstream DNS over Discord docs, with user-installation (https://github.com/MattIPv4/DNS-over-Discord/pull/89) + DNSSEC disabling (https://github.com/MattIPv4/DNS-over-Discord/pull/65)

Screenshots (optional)

N/A

Documentation checklist

• [x] The documentation style guide has been adhered to.
• [ ] If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• [ ] Files which have changed name or location have been allocated redirects.