add IDL and Mojo to glossary (#12504)

docs/glossary.md

@@ -35,6 +35,10 @@ Input Method Editor. A program that allows users to enter characters and
 symbols not found on their keyboard. For example, this allows users of Latin
 keyboards to input Chinese, Japanese, Korean and Indic characters.
 
+### IDL
+
+Interface description language. Write function signatures and data types in a format that can be used to generate interfaces in Java, C++, JavaScript, etc.
+
 ### IPC
 
 IPC stands for Inter-Process Communication. Electron uses IPC to send
@@ -68,6 +72,12 @@ See also: [process](#process), [renderer process](#renderer-process)
 Acronym for Apple's Mac App Store. For details on submitting your app to the
 MAS, see the [Mac App Store Submission Guide].
 
+### Mojo
+
+An IPC system for communicating intra- or inter-process, and that's important because Chrome is keen on being able to split its work into separate processes or not, depending on memory pressures etc. 
+
+See https://chromium.googlesource.com/chromium/src/+/master/mojo/README.md
+
 ### native modules
 
 Native modules (also called [addons] in