Add support for a "C++" tag name

parser/examples/tags.md

@@ -10,7 +10,7 @@ With #several #tags mentioned
 
 #Order is preserved.
 This is a tag in quotes "#1-1"
-#C# is a valid tag.
+#C# and #C++ are valid tags.
 Tag in a URL: http://example.com/#foo
 
 \#ignored

parser/parser_test.go

@@ -43,11 +43,11 @@ func TestParseDuplicateTags(t *testing.T) {
 	got := Parse("examples/tags.md")
 	want := []Note{
 		{
-			Content: "This is a #test file. #test\nWith #several #tags mentioned\n#several times.\n\n## Subheading\n\n#Order is preserved.\nThis is a tag in quotes \"#1-1\"\n#C# is a valid tag.\nTag in a URL: http://example.com/#foo\n\n\\#ignored",
+			Content: "This is a #test file. #test\nWith #several #tags mentioned\n#several times.\n\n## Subheading\n\n#Order is preserved.\nThis is a tag in quotes \"#1-1\"\n#C# and #C++ are valid tags.\nTag in a URL: http://example.com/#foo\n\n\\#ignored",
 			File:    "examples/tags.md",
 			Id:      202204192322,
 			Links:   nil,
-			Tags:    []string{"#test", "#several", "#tags", "#Order", "#C#"},
+			Tags:    []string{"#test", "#several", "#tags", "#Order", "#C#", "#C++"},
 			Title:   "Test tags mentioned multiple times",
 		},
 	}

util/util.go

@@ -11,7 +11,7 @@ var LinkRegex *regexp.Regexp
 
 func init() {
 	IdRegex = regexp.MustCompile(`^(\d{12})$`)
-	TagRegex = regexp.MustCompile(`(?:^|\s+)(#+\.?[0-9a-zA-Z_-][#0-9a-zA-Z_-]+)`)
+	TagRegex = regexp.MustCompile(`(?:^|\s+)(#+\.?[0-9a-zA-Z_-][#0-9a-zA-Z_\-+]+)`)
 	LinkRegex = regexp.MustCompile(`\B\[\[([\d\s\/:]+)\]\]`)
 }