Restructure documentation. Now the documentation has installation, administration, usage, development, contributing the 5 main parts (#23629)

- **Installation**: includes how to install Gitea and related other
tools, also includes upgrade Gitea
- **Administration**: includes how to configure Gitea, customize Gitea
and manage Gitea instance out of Gitea admin UI
- **Usage**: includes how to use Gitea's functionalities. A sub
documentation is about packages, in future we could also include CI/CD
and others.
- **Development**: includes how to integrate with Gitea's API, how to
develop new features within Gitea
- **Contributing**: includes how to contribute code to Gitea
repositories.

After this is merged, I think we can have a sub-documentation of `Usage`
part named `Actions` to describe how to use Gitea actions

---------

Co-authored-by: John Olheiser <john.olheiser@gmail.com>

Makefile

@@ -77,6 +77,7 @@ ifeq ($(RACE_ENABLED),true)
 endif
 
 STORED_VERSION_FILE := VERSION
+HUGO_VERSION ?= 0.111.3
 
 ifneq ($(DRONE_TAG),)
 	VERSION ?= $(subst v,,$(DRONE_TAG))
@@ -817,7 +818,7 @@ release-docs: | $(DIST_DIRS) docs
 .PHONY: docs
 docs:
 	@hash hugo > /dev/null 2>&1; if [ $$? -ne 0 ]; then \
-		curl -sL https://github.com/gohugoio/hugo/releases/download/v0.74.3/hugo_0.74.3_Linux-64bit.tar.gz | tar zxf - -C /tmp && mv /tmp/hugo /usr/bin/hugo && chmod +x /usr/bin/hugo; \
+		curl -sL https://github.com/gohugoio/hugo/releases/download/v$(HUGO_VERSION)/hugo_$(HUGO_VERSION)_Linux-64bit.tar.gz | tar zxf - -C /tmp && mv /tmp/hugo /usr/bin/hugo && chmod +x /usr/bin/hugo; \
 	fi
 	cd docs; make trans-copy clean build-offline;