docs(functions): merge manual-only examples and notes into headers

Folds the examples Section 5 carried but the headers did not into each
function's `# EXAMPLE`, and moves the three lines that only looked like
examples -- the two typo-abbreviation notes and rm's /usr/bin/rm fallback --
into `# NOTES`, the label already in use.

Also corrects gi's synopsis, which omitted -l, and documents yt-dlp's
--no-embed-thumbnail in `# ARGUMENTS`.

functions/spark.fish

@@ -22,6 +22,7 @@
 # EXAMPLE
 #   spark 1 1 2 5 14 42
 #   seq 64 | sort --random-sort | spark
+#   echo "3 7 2 9 1" | spark
 function spark --description 'Sparklines'
     argparse --ignore-unknown --name=spark v/version h/help m/min= M/max= -- $argv || return