fix: dockerfile tooltips should match only keywords

Before this change, the Dockerfile tooltip script marked all occurences
of keywords, as defined by the lexer, as Dockerfile instructions in a
`dockerfile` code block. This meant some tokens parsed from heredocs
would be included. The matched keyword token is now compared against a
hard-coded list of actual Dockerfile instructions before they're
annotated.

Signed-off-by: David Karlsson <35727626+dvdksn@users.noreply.github.com>

assets/js/src/tooltip.js

@@ -1,4 +1,25 @@
-const cmds = document.querySelectorAll(".language-dockerfile span.k");
+const keywords = [
+  "ADD",
+  "ARG",
+  "CMD",
+  "COPY",
+  "ENTRYPOINT",
+  "ENV",
+  "EXPOSE",
+  "FROM",
+  "HEALTHCHECK",
+  "LABEL",
+  // "MAINTAINER",
+  "ONBUILD",
+  "RUN",
+  "SHELL",
+  "STOPSIGNAL",
+  "USER",
+  "VOLUME",
+  "WORKDIR",
+]
+const cmds = Array.from(document.querySelectorAll(".language-dockerfile span.k"))
+  .filter((el) => keywords.some(kwd => el.textContent.includes(kwd)));
 
 for (const cmd of cmds) {
   const name = cmd.textContent;