add \B, fix lb and rb

static/js/libs/katex.js

@@ -5,6 +5,7 @@ window.addEventListener("load", () => {
       N: "mathbb{N}",
       R: "mathbb{R}",
       Z: "mathbb{Z}",
+      B: "mathbb{B}",
       O: "Theta",
       ra: "rightarrow",
       la: "leftarrow",
@@ -12,8 +13,8 @@ window.addEventListener("load", () => {
       LA: "Leftarrow",
       u: "mu",
       Tau: "mathrm{T}",
-      lb: "textlbrackdbl",
-      rb: "textrbrackdbl",
+      lb: "llbracket",
+      rb: "rrbracket",
     })
   )[Symbol.iterator]()) {
     const bs = "\\";