docs: Update mkdocs styling (#5119)

This adds a better style for the whole page with most visible piece being the logo, but it also prepares the code for further modifications.

* Increased font weight
* Added additional configurable mkdocs variables
* New images for the logo
* Added custom grass properties with gs prefix

---------

Co-authored-by: Corey White <[email protected]>

man/Makefile

@@ -14,7 +14,9 @@ DSTFILES := \
 	$(HTMLDIR)/parser_standard_options.css \
 	$(HTMLDIR)/parser_standard_options.js \
 	$(MDDIR)/mkdocs.yml \
-	$(MDDIR)/source/grass_logo.png \
+	$(MDDIR)/source/grass_logo.svg \
+	$(MDDIR)/source/grass_icon.png \
+	$(MDDIR)/source/favicon.ico \
 	$(MDDIR)/source/grassdocs.css \
 	$(MDDIR)/scripts/hook_list_scripts.py \
 	$(MDDIR)/overrides/partials/footer.html \
@@ -223,9 +225,6 @@ $(HTMLDIR)/grassdocs.css: grassdocs.css
 $(HTMLDIR)/grass_logo.png: grass_logo.png
 	$(INSTALL_DATA) $< $@
 
-$(MDDIR)/source/grass_logo.png: grass_logo.png
-	$(INSTALL_DATA) $< $@
-
 $(HTMLDIR)/hamburger_menu.svg: hamburger_menu.svg
 	$(INSTALL_DATA) $< $@
 
@@ -247,6 +246,15 @@ $(HTMLDIR)/parser_standard_options.css: parser_standard_options.css
 $(MDDIR)/mkdocs.yml: mkdocs/mkdocs.yml
 	$(INSTALL_DATA) $< $@
 
+$(MDDIR)/source/grass_logo.svg: grass_logo.svg
+	$(INSTALL_DATA) $< $@
+
+$(MDDIR)/grass_icon.png: grass_icon.png
+	$(INSTALL_DATA) $< $@
+
+$(MDDIR)/source/favicon.ico: favicon.ico
+	$(INSTALL_DATA) $< $@
+
 $(MDDIR)/source/grassdocs.css: mkdocs/grassdocs.css
 	$(INSTALL_DATA) $< $@