feat: improved TextMate grammar (#623)

### Summary of Changes

Various improvements to the auto-generated TextMate grammar:
* Categorization of keywords into correct groups
* Description of number literals
* Treatment of keywords that are enclosed in backticks as names
* Test markers are no longer treated as comments

.gitignore

@@ -12,7 +12,7 @@ dist/
 dist-ssr/
 generated/
 out/
-syntaxes/safe-ds.tmLanguage.json
+syntaxes/safe-ds.generated.tmLanguage.json
 
 # Node
 .npm/

langium-config.json

@@ -6,7 +6,7 @@
             "grammar": "src/language/grammar/safe-ds.langium",
             "fileExtensions": [".sdspipe", ".sdsstub", ".sdstest"],
             "textMate": {
-                "out": "syntaxes/safe-ds.tmLanguage.json"
+                "out": "syntaxes/safe-ds.generated.tmLanguage.json"
             }
         }
     ],

syntaxes/safe-ds.tmLanguage.json

@@ -0,0 +1,88 @@
+{
+  "name": "safe-ds",
+  "scopeName": "source.safe-ds",
+  "fileTypes": [
+    ".sdspipe",
+    ".sdsstub",
+    ".sdstest"
+  ],
+  "patterns": [
+    {
+      "include": "#comments"
+    },
+    {
+      "name": "constant.numeric.safe-ds",
+      "match": "\\b([0-9]+(\\.[0-9]+)?([eE][+-]?[0-9]+)?)\\b"
+    },
+    {
+      "name": "constant.language.safe-ds",
+      "match": "\\b(false|null|true)\\b"
+    },
+    {
+      "name": "storage.type.safe-ds",
+      "match": "\\b(annotation|attr|class|enum|fun|package|pipeline|schema|segment|val)\\b"
+    },
+    {
+      "name": "storage.modifier.safe-ds",
+      "match": "\\b(const|in|internal|out|private|static)\\b"
+    },
+    {
+      "name": "keyword.operator.safe-ds",
+      "match": "\\b(and|not|or|sub|super)\\b"
+    },
+    {
+      "name": "keyword.other.safe-ds",
+      "match": "\\b(as|from|import|literal|union|where|yield)\\b"
+    },
+    {
+      "name": "entity.name.safe-ds",
+      "begin": "\\`",
+      "end": "\\`"
+    },
+    {
+      "name": "string.quoted.double.safe-ds",
+      "begin": "\"",
+      "end": "\"",
+      "patterns": [
+        {
+          "include": "#string-character-escape"
+        }
+      ]
+    }
+  ],
+  "repository": {
+    "comments": {
+      "patterns": [
+        {
+          "name": "comment.line.double-slash.safe-ds",
+          "begin": "//",
+          "beginCaptures": {
+            "1": {
+              "name": "punctuation.whitespace.comment.leading.safe-ds"
+            }
+          },
+          "end": "(?=$)"
+        },
+        {
+          "name": "comment.block.safe-ds",
+          "begin": "/\\*",
+          "beginCaptures": {
+            "0": {
+              "name": "punctuation.definition.comment.safe-ds"
+            }
+          },
+          "end": "\\*/",
+          "endCaptures": {
+            "0": {
+              "name": "punctuation.definition.comment.safe-ds"
+            }
+          }
+        }
+      ]
+    },
+    "string-character-escape": {
+      "name": "constant.character.escape.safe-ds",
+      "match": "\\\\(x[0-9A-Fa-f]{2}|u[0-9A-Fa-f]{4}|u\\{[0-9A-Fa-f]+\\}|[0-2][0-7]{0,2}|3[0-6][0-7]?|37[0-7]?|[4-7][0-7]?|.|$)"
+    }
+  }
+}