[ENH] Add example config for deploying a node behind NGINX and clarify data uploading

[alyssadai]

• Closes Add example docker-compose.yml variation with NGINX+ACME #239
• Closes Add a deployable docker compose recipe that includes reverse proxy and SSL recipes#93

Changes proposed in this pull request:

• Add new section "Behind a proxy" with example docker-compose.yml including NGINX+ACME
• Restructure "Updating data in the graph" section slightly, and link to it more explicitly in the Getting Started steps, to further centralize and make intuitive the key steps for setting up a database. This:
  • avoids the complexity of having to link to both https://neurobagel.org/getting_started/#the-neurobagel-node-deployment-recipe and https://neurobagel.org/maintaining/#updating-the-data-in-your-graph whenever we want to refer to a complete node setup (e.g., in this PR, following the old structure, it was difficult to tie in the customized NGINX docker-compose.yml back to the rest of the node setup steps without having to reference multiple different sections)
  • provides a more straightforward workflow for users who completed the annotation process first (related: Add "Getting started" docs route for users who already have JSONLD data #202)
• Differentiate names of sections relating to updating graph data to avoid confusion, and fix outdated links pointing to manual setup instructions
• Fix some indenting in admonitions

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[surchs]

Thanks @alyssadai for addressing this quickly. Text looks great.

I'm neutral on adding the 4th point to the getting-started section, but OK to go with your opinion here (we can also ask users to tell us if that's clear).

One suggestion, then 🧑‍🍳