Added cursor_token_match util file

app/javascript/gabsocial/utils/cursor_token_match.js

@@ -0,0 +1,26 @@
+'use strict';
+
+export function textAtCursorMatchesToken(str, caretPosition, searchTokens) {
+  let word;
+
+  let left = str.slice(0, caretPosition).search(/\S+$/);
+  let right = str.slice(caretPosition).search(/\s/);
+
+  if (right < 0) {
+    word = str.slice(left);
+  } else {
+    word = str.slice(left, right + caretPosition);
+  }
+
+  if (!word || word.trim().length < 3 || searchTokens.indexOf(word[0]) === -1) {
+    return [null, null];
+  }
+
+  word = word.trim().toLowerCase();
+
+  if (word.length > 0) {
+    return [left + 1, word];
+  }
+
+  return [null, null];
+};