config: use inline math and common characters

Latex errors cannot be parsed by humans, so just use inline math which we had working elsewhere already.

Also use simplified character for ế, for latex compatibility.

.vscode/settings.json

@@ -14,7 +14,7 @@
          "**/_version.py",
     ],
     "spellright.ignoreRegExps": [
-        "/.. math::[^]*?.. endmath/gm",
+        "/:math:`[^]*?`/gm",
         "/``[^]*?``/gm",
         "/'[^]*?'/gm",
         "/.. data:: [^]*?'*$/gm",