docs: add make command to deploy docs to readme
docs: add logo to first page
docs: fix: remove www/ prefix in link to gif
docs: use logo.svg as favicon
docs: add date and version in footer
docs: change home page icon

The unicode symbol is not available in all fonts.
Replace it with a more common one.
docs: inject version into full page, not main
docs: simplify title manipulation in script
docs: improve css styling
docs: use pipx in installation instructions

Some distributions (incl. Debian, Alpine) no longer allow
"user installations" with pip.
makefile: rearrange targets to build docs
docs: fix: add css for gif figure
makefile: point to python3 explicitly
docs: add manual.md pointing to man page

This is for those browsing the docs in markdown format
on the code forge site.
On the HTML site built using the makefile,
the link on the installation page points directly
to the HTML version of the manpage.
docs: minor corrections
docs: add gif to first page
docs: add link to online docs in readme
docs: add logo svg
docs: add usage gif

The GIF was created by taking a succession of screenshots
and composing them as follows:

    sudo apt install graphicsmagick gifsicle
    gm convert 0{1..7}.png -delay 80 01-07.gif
    gm convert 07.png \
        -compose Atop -page +100+40 08.png \
        -flatten 08.gif
    gifsicle --use-colormap web -O3 --loop \
        01-07.gif -d960 08.gif > usage.gif
make: Add task to upload docs to pages.sr.ht