[mlir-vscode] Add support for highlighting pdll and tablegen markdown code blocks

[rriddle]

Summary

This essentially just piggy backs off of the existing mlir support.

[jpienaar]

Nice (which reminds me I need to update the injection in another spot post https://github.com/llvm/llvm-project/commit/999fb7d0450a804f3eb0d16d2853e8667658f39e)

mlir/utils/vscode/markdown-grammar.json

 {
   "fileTypes": [],
   "injectionSelector": "L:text.html.markdown",
   "patterns": [
     {
       "include": "#mlir-code-block"
+    },
+    {
+      "include": "#pdll-code-block"
+    },
+    {
+      "include": "#tablegen-code-block"
     }
   ],
   "repository": {
     "mlir-code-block": {
       "begin": "(^|\\G)(\\s*)(\\`{3,}|~{3,})\\s*(?i:(mlir)(\\s+[^`~]*)?$)",
       "name": "markup.fenced_code.block.markdown",
       "end": "(^|\\G)(\\2|\\s{0,3})(\\3)\\s*$",
       "beginCaptures": {
"mlir-code-block": {
           "contentName": "meta.embedded.block.mlir",
           "patterns": [
             {
               "include": "source.mlir"
             }
           ]
         }
       ]
+    },
+    "pdll-code-block": {
+      "begin": "(^|\\G)(\\s*)(\\`{3,}|~{3,})\\s*(?i:(pdll)(\\s+[^`~]*)?$)",
+      "name": "markup.fenced_code.block.markdown",
+      "end": "(^|\\G)(\\2|\\s{0,3})(\\3)\\s*$",
+      "beginCaptures": {
+        "3": {
+          "name": "punctuation.definition.markdown"
+        },
+        "4": {
+          "name": "fenced_code.block.language.markdown"
+        },
+        "5": {
+          "name": "fenced_code.block.language.attributes.markdown"
+        }
+      },
+      "endCaptures": {
+        "3": {
+          "name": "punctuation.definition.markdown"
+        }
+      },
+      "patterns": [
+        {
+          "begin": "(^|\\G)(\\s*)(.*)",
+          "while": "(^|\\G)(?!\\s*([`~]{3,})\\s*$)",
+          "contentName": "meta.embedded.block.pdll",
+          "patterns": [
+            {
+              "include": "source.pdll"
+            }
+          ]
+        }
+      ]
+    },
+    "tablegen-code-block": {
+      "begin": "(^|\\G)(\\s*)(\\`{3,}|~{3,})\\s*(?i:(tablegen)(\\s+[^`~]*)?$)",
+      "name": "markup.fenced_code.block.markdown",
+      "end": "(^|\\G)(\\2|\\s{0,3})(\\3)\\s*$",
+      "beginCaptures": {
+        "3": {
+          "name": "punctuation.definition.markdown"
+        },
+        "4": {
+          "name": "fenced_code.block.language.markdown"
+        },
+        "5": {
+          "name": "fenced_code.block.language.attributes.markdown"
+        }
+      },
+      "endCaptures": {
+        "3": {
+          "name": "punctuation.definition.markdown"
+        }
+      },
+      "patterns": [
+        {
+          "begin": "(^|\\G)(\\s*)(.*)",
+          "while": "(^|\\G)(?!\\s*([`~]{3,})\\s*$)",
+          "contentName": "meta.embedded.block.tablegen",
+          "patterns": [
+            {
+              "include": "source.tablegen"
+            }
+          ]
+        }
+      ]
     }
   },
   "scopeName": "markdown.mlir.codeblock"
 }
 No newline at end of file

mlir/utils/vscode/package.json

"grammars": [
       {
         "language": "mlir-injection",
         "scopeName": "markdown.mlir.codeblock",
         "path": "markdown-grammar.json",
         "injectTo": [
           "text.html.markdown"
         ],
         "embeddedLanguages": {
-          "meta.embedded.block.mlir": "mlir"
+          "meta.embedded.block.mlir": "mlir",
+          "meta.embedded.block.pdll": "pdll",
+          "meta.embedded.block.tablegen": "tablegen"
         }
       },
       {
         "scopeName": "source.cpp.mlir",
         "path": "./cpp-grammar.json",
         "injectTo": [
           "source.cpp"
         ],