[feature-request] add 'when-let' and 'if-let'

[rhcher]

Hi, thank you for your great work. recently aniseed and conjure add when-let and if-let macro. I just add them in
highlights.scm, is this correct?

diff --git a/after/queries/fennel/highlights.scm b/after/queries/fennel/highlights.scm
index ac997a3..3b0f979 100644
--- a/after/queries/fennel/highlights.scm
+++ b/after/queries/fennel/highlights.scm
@@ -5,7 +5,7 @@
 
 ((list .
    (symbol) @keyword)
- (#any-of? @keyword "def" "def-"))
+ (#any-of? @keyword "def" "def-" "when-let" "if-let"))
 
 ((symbol) @include (#eq? @include "autoload"))