chore: proper version control of Tailwind

It was a mistake of me to not insist on proper version control
of Tailwind from the start.

The result was that the colors subtly changed between v1 and v2 of
Tailwind, and the whole website would be styled to the colors of
the version of Tailwind that the last person to run `generate-css`
happened to have on their machine.

That's not great!

Instead, now do proper version control by using `package.json`,
and control the version of Tailwind we use.

For now, we settle on Tailwind v1, because it has the colors we
want. We could eventually decide to move to Tailwind v2, if we find
a way to restore the old colors.

For now, there doesn't seem to be a pressing reason to upgrade, so
this is the simplest way to get the result we want. We can always
consciously decide to upgrade later.

tailwind/.gitignore

@@ -0,0 +1 @@
+node_modules

tailwind/generate-css

@@ -1,20 +1,11 @@
 #!/bin/bash
 set -eu
+scriptdir=$(cd $(dirname $0) && pwd)
+cd $scriptdir
 
-if ! which tailwindcss > /dev/null; then
-  echo "This script needs Tailwind installed." >&2
-  echo "Run 'npm install -g tailwindcss autoprefixer postcss' and try again." >&2
-  exit 1
-fi
+# Install the dependencies at the versions indicated by package.json and package-lock.json
+npm ci
 
-if ! which minify > /dev/null; then
-  echo "This script needs minify installed." >&2
-  echo "Run 'npm install -g minify' and try again." >&2
-  exit 1
-fi
-
-cd $(dirname $0)
-
-tailwindcss build styles.css -o ../static/css/generated.css
-minify ../static/css/generated.css > ../static/css/generated.css.min
+npx tailwindcss build styles.css -o ../static/css/generated.css
+npx minify ../static/css/generated.css > ../static/css/generated.css.min
 mv ../static/css/generated.css{.min,}