Remove fontimage.png from npm package

It turned out that README in npm registry page cannot show images in the
package and the only one way is to host images somewhere and refer to
the URLs. It is okay to revert the image reference in README-npm.md for
now.

README-npm.md

@@ -2,7 +2,7 @@
 
 This is a handwritten font created by @saltcandy123.
 
-![Font image](./fontimage.png)
+![Font image](https://raw.githubusercontent.com/saltcandy123/saltcandy123font/main/fontimage.png)
 
 ## Usage
 

scripts/build-dist.sh

@@ -19,7 +19,6 @@ NPM_PACKAGE_DIR="${DIST_DIR}/npm-package"
 mkdir -p "${NPM_PACKAGE_DIR}"
 cp "${DIST_DIR}/saltcandy123font.ttf" "${DIST_DIR}/saltcandy123font.woff" "${NPM_PACKAGE_DIR}/"
 cp "${BASE_DIR}/README-npm.md" "${NPM_PACKAGE_DIR}/README.md"
-bash "${BASE_DIR}/scripts/generate-fontimage.sh" "${DIST_DIR}/saltcandy123font.ttf" "${NPM_PACKAGE_DIR}/fontimage.png"
 cat <<EOF | python -m json.tool >"${NPM_PACKAGE_DIR}/package.json"
 {
     "name": "@saltcandy123/saltcandy123font",