New IA implementation

Reference: [#110](https://github.com/etcd-io/website/issues/110), [#65](https://github.com/etcd-io/website/issues/65)

## Permalink Structure

- [x] Blog (/blog)
- [x] **Community** (/community) #306
- [ ] **Contributor Guide** (/docs/contributor-guide) -- either as a separate page or embedded in Community #400
- [ ] _Issue Triage Guidelines_ (/docs/contributor-guide/issues)
- [ ] _Reporting bugs_ (/docs/contributor-guide/reporting_bugs)
- [ ] Docs (/docs Documentation ToC)
- [x] v3.5† (docs/v3.5) [#363](https://github.com/etcd-io/website/pull/363)
- [ ] Administration (/docs/v3.5/administration) #401
- [x] **Quickstart** (/docs/v3.5/quickstart) #218, #278
- [x] **Install** (/docs/v3.5/install) #318
- [ ] **Troubleshooting etcd** (/docs/v3.5/troubleshooting) #395
- [x] ~~Overview (/docs/v3.5/rfc/v3api/)~~ [#364](https://github.com/etcd-io/website/pull/364)
- [ ] ~~Demo~~ (/docs/v3.5/demo) (Rework into _Tutorials_ section) #402
- [x] ~~Download and build~~ (docs/v3.5/dl-build) (Refactor into _Quickstart_ and _Installation_) #319
- [ ] FAQ (/docs/v3.5/faq)
- [ ] Branch management (/docs/v3.5/branch_management)
- [ ] Libraries and tools (/docs/v3.5/integrations)
- [ ] Metrics (/docs/v3.5/metrics)
- [ ] ~~Reporting bugs~~ (/docs/v3.5/reporting_bugs) #400
- [ ] Tuning (/docs/v3.5/tuning)
- [ ] Discovery service protocol (/docs/v3.5/dev-internal/discovery_protocol)
- [ ] etcd release guide (/docs/v3.5/dev-internal/release)
- [ ] Logging conventions (/docs/v3.5/dev-internal/logging)
- [ ] Learning (/docs/v3.5/learning)
- [ ] ⋮
- [ ] **Tutorials** (/docs/v3.5/tutorials) #402
- [ ] ⋮
- [ ] Developer Guide (/docs/v3.5/dev-guide)
- [ ] ⋮
- [ ] Operations Guide (/docs/v3.5/op-guide)
- [ ] ⋮
- [ ] Benchmarks (/docs/v3.5/benchmarks)
- [ ] ⋮
- [ ] Upgrading (/docs/v3.5/upgrades)
- [ ] ⋮
- [ ] ~~Platforms~~‡ (/docs/v3.5/platforms) (#396, #397, #398, #399)
- [ ] ⋮
- [ ] ~~Triage~~ (/docs/v3.5/triage)
- [ ] ~~Issue Triage Guidelines~~ (/docs/v3.5/triage/issues) #400
- [ ] ⋮ (versions 2.3 & 3.1-3.4)

#### Legend

**Bold**: new pages
_Italic_: moved pages (new location)
~~Strike through~~: moved or removed pages (old location)
⋮ (vertical ellipsis): one or more unlisted pages

#### Notes

> † v3.5 expanded as an example. v3.5 and v3.4 currently share the same architecture, but may differ in future.
> ‡ Content under Platforms should be reworked and made into blog posts. (Amazon Web Services, Container Linux with systemd, FreeBSD)

Other:

- [x] Top nav, see #341
- [ ] Homepage: adjustments to be done based on the IA implementation detailed above.