Add Grimmory subdomain config

[NaruZosa]

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

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Description

Adds a sample subdomain config for Grimmory.

Benefits of this PR and context

Grimmory is a maintained fork of Booklore, which had a sample config requested in #770

Please note that the Kobo integration docs specify Nginx requires the following settings:

proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Forwarded-Port $server_port;

proxy_buffer_size 128k;
proxy_buffers 4 256k;
proxy_busy_buffers_size 256k;
large_client_header_buffers 8 32k;

The sample config includes these, and is functional. When testing without these settings, syncing on my Kobo failed and SWAG logged the following error:
[error] 617761#617761: *7653 upstream sent too big header while reading response header from upstream, client: <REDACTED_IP>, server: grimmory.*, request: "GET /api/kobo/<REDACTED_API_TOKEN>/v1/library/sync?Filter=ALL&DownloadUrlFilter=Generic,Android&PrioritizeRecentReads=true HTTP/1.1", upstream: "http://<CONTAINER_IP>:6060/api/kobo/<REDACTED_API_TOKEN>/v1/library/sync?Filter=ALL&DownloadUrlFilter=Generic,Android&PrioritizeRecentReads=true", host: "grimmory.<REDACTED_DOMAIN>.com"

These settings conflict with /config/nginx/proxy.conf so the location /api/kobo/ does not include the line include /config/nginx/proxy.conf;.

How Has This Been Tested?

Tested and in active use on my instance, including the Kobo sync integration.

Source / References