Explicitly add terser to node_modules/

While we were already including terser as a transitive dependency
via rollup-plugin-terser, the resolved version was quite old.
By explicitly adding terser to our node_modules deps, we can ensure
we are using a recent version.

R=aerotwist@chromium.org

Bug: none
Change-Id: Ie10a808ce3cbe80138183a9704816aa966a01f16
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2975283
Reviewed-by: Paul Lewis <aerotwist@chromium.org>
Commit-Queue: Paul Lewis <aerotwist@chromium.org>
Auto-Submit: Tim van der Lippe <tvanderlippe@chromium.org>

node_modules/terser/tools/domprops.js

@@ -4120,6 +4120,7 @@ export var domprops = [
     "exponent",
     "exponentialRampToValueAtTime",
     "exportKey",
+    "exports",
     "extend",
     "extensions",
     "extentNode",

node_modules/terser/tools/terser.d.ts

@@ -96,6 +96,7 @@ export interface ManglePropertiesOptions {
 
 export interface FormatOptions {
     ascii_only?: boolean;
+    /** @deprecated Not implemented anymore */
     beautify?: boolean;
     braces?: boolean;
     comments?: boolean | 'all' | 'some' | RegExp | ( (node: any, comment: {