quarto: default name should default to directory name when using index.qmd

[aronatkins]

mkdir VeryInteresting
cd VeryInteresting
echo "very interesting" > index.qmd
rsconnect deploy quarto index.qmd

The content name should default to "VeryInteresting" rather than "index".

[aronatkins]

Alternatively, extract the title from the YAML preamble.

[aronatkins]

When deploying with an _quarto.yml file, extract the title from that file, if available, falling back to the title in the index.qmd.