Syntax highlight fixes for quoted codes and aliases after keywords

[jafeltra]

Fixes #72

This PR fixes the issue reported in #72. With the current version of the extension, having a coding with a system that uses an alias and a code that has spaces does not highlight correctly. With this branch, the following rule no longer breaks the syntax highlighting for the rest of the file:

* valueCodeableConcept = $test#"example code"

I also made a bonus update to an issue that I saw recently. When using an Alias that starts with $ after a FSH keyword, it wasn't highlighted. If this shouldn't have been highlighted, I can revert this change. With this branch, the following keyword highlight as expected:

InstanceOf: $ServiceRequest

I checked and neither of these issues appear on FSH Online because it uses slightly different syntax highlighting.

I also ran an npm audit fix and committed those changes, and I had to update the @vscode/test-electron dependency to get the tests to run again.

[cmoesel]

This probably fits into the category of "just be happy it doesn't break" -- but I noticed inconsistency in the highlighing:

• URL system and unquoted code is all brown
• URL system and quoted code has brown system, green #, and green code
• Alias and unquoted code is all green
• Alias and quoted code has green alias, brown #, and brown code

So basically, it's totally different across each of those 4 possible cominations. Did you see this? Do we care?

[jafeltra]

Alrighty, I was tempted to say we don't care, but really I did care. I think that pattern of mismatched highlighting has actually been around for a long time, but I think I found a pretty easy way to address it. I did two things to get the highlighting to be consistent:

• I made it so that aliases that start with $ ($abc) are highlighted brown like URLs are. I thought that made sense since they represent URLs. I also made it so that the match for those ends with a space or a # since that's where an alias ends and either a new word or a code starts. That's dca537c.
• I made it so we don't highlight fragments that are part of URLs. Technically a # can be part of a valid URL, which is why it had previously been in our regular expression for matching URLs. However, it seemed like it would be much more common in FSH to have a URL without a fragment and with a code. I couldn't think of a way to distinguish a URL ending with a fragment and a URL system with a code. So I decided to remove the # from the regular expression for a URL, that way we can highlight the URL portion brown and highlight the code portion green. I think this could lead to some mildly confusing highlighting when creating an Alias with a url that has a fragment, but I decided I was okay with that. Let me know if you are also okay with that. That's ac66df9.

[cmoesel]

Alright! These look good to me! Thanks for doing the bonus round as well!