Bump handlebars from 4.0.11 to 4.1.2 in /demo

Bumps [handlebars](https://github.com/wycats/handlebars.js) from 4.0.11 to 4.1.2.
- [Release notes](https://github.com/wycats/handlebars.js/releases)
- [Changelog](https://github.com/wycats/handlebars.js/blob/master/release-notes.md)
- [Commits](handlebars-lang/handlebars.js@v4.0.11...v4.1.2)

Signed-off-by: dependabot[bot] <support@github.com>

demo/yarn.lock

@@ -93,10 +93,6 @@ alphanum-sort@^1.0.1, alphanum-sort@^1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/alphanum-sort/-/alphanum-sort-1.0.2.tgz#97a1119649b211ad33691d9f9f486a8ec9fbe0a3"
 
-amdefine@>=0.0.4:
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/amdefine/-/amdefine-1.0.1.tgz#4a5282ac164729e93619bcfd3ad151f817ce91f5"
-
 ansi-align@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/ansi-align/-/ansi-align-2.0.0.tgz#c36aeccba563b89ceb556f3690f0b1d9e3547f7f"
@@ -296,7 +292,7 @@ async@2.6.0, async@^2.1.2, async@^2.1.4, async@^2.4.1:
   dependencies:
     lodash "^4.14.0"
 
-async@^1.4.0, async@^1.5.2:
+async@^1.5.2:
   version "1.5.2"
   resolved "https://registry.yarnpkg.com/async/-/async-1.5.2.tgz#ec6a61ae56480c0c3cb241c95618e20892f9672a"
 
@@ -1568,6 +1564,10 @@ commander@2.15.x, commander@^2.11.0, commander@~2.15.0:
   version "2.15.1"
   resolved "https://registry.yarnpkg.com/commander/-/commander-2.15.1.tgz#df46e867d0fc2aec66a34662b406a9ccafff5b0f"
 
+commander@~2.20.0:
+  version "2.20.0"
+  resolved "https://registry.yarnpkg.com/commander/-/commander-2.20.0.tgz#d58bb2b5c1ee8f87b0d340027e9e94e222c5a422"
+
 commondir@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/commondir/-/commondir-1.0.1.tgz#ddd800da0c66127393cca5950ea968a3aaf1253b"
@@ -3074,14 +3074,14 @@ handle-thing@^1.2.5:
   resolved "https://registry.yarnpkg.com/handle-thing/-/handle-thing-1.2.5.tgz#fd7aad726bf1a5fd16dfc29b2f7a6601d27139c4"
 
 handlebars@^4.0.3:
-  version "4.0.11"
-  resolved "https://registry.yarnpkg.com/handlebars/-/handlebars-4.0.11.tgz#630a35dfe0294bc281edae6ffc5d329fc7982dcc"
+  version "4.1.2"
+  resolved "https://registry.yarnpkg.com/handlebars/-/handlebars-4.1.2.tgz#b6b37c1ced0306b221e094fc7aca3ec23b131b67"
   dependencies:
-    async "^1.4.0"
+    neo-async "^2.6.0"
     optimist "^0.6.1"
-    source-map "^0.4.4"
+    source-map "^0.6.1"
   optionalDependencies:
-    uglify-js "^2.6"
+    uglify-js "^3.1.4"
 
 har-schema@^2.0.0:
   version "2.0.0"
@@ -4636,9 +4636,9 @@ negotiator@0.6.1:
   version "0.6.1"
   resolved "https://registry.yarnpkg.com/negotiator/-/negotiator-0.6.1.tgz#2b327184e8992101177b28563fb5e7102acd0ca9"
 
-neo-async@^2.5.0:
-  version "2.5.1"
-  resolved "https://registry.yarnpkg.com/neo-async/-/neo-async-2.5.1.tgz#acb909e327b1e87ec9ef15f41b8a269512ad41ee"
+neo-async@^2.5.0, neo-async@^2.6.0:
+  version "2.6.1"
+  resolved "https://registry.yarnpkg.com/neo-async/-/neo-async-2.6.1.tgz#ac27ada66167fa8849a6addd837f6b189ad2081c"
 
 next-tick@1:
   version "1.0.0"
@@ -5670,7 +5670,7 @@ react-icons@^2.2.7:
     react-icon-base "2.1.0"
 
 react-piano@../:
-  version "2.0.1"
+  version "3.1.2"
   dependencies:
     classnames "^2.2.6"
     just-range "^2.1.0"
@@ -6341,12 +6341,6 @@ source-map@0.5.x, source-map@^0.5.3, source-map@^0.5.6, source-map@^0.5.7, sourc
   version "0.5.7"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.5.7.tgz#8a039d2d1021d22d1ea14c80d8ea468ba2ef3fcc"
 
-source-map@^0.4.4:
-  version "0.4.4"
-  resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.4.4.tgz#eba4f5da9c0dc999de68032d8b4f76173652036b"
-  dependencies:
-    amdefine ">=0.0.4"
-
 source-map@^0.6.1, source-map@~0.6.1:
   version "0.6.1"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.6.1.tgz#74722af32e9614e9c287a8d0bbde48b5e2f1a263"
@@ -6779,7 +6773,7 @@ uglify-js@3.3.x, uglify-js@^3.0.13:
     commander "~2.15.0"
     source-map "~0.6.1"
 
-uglify-js@^2.6, uglify-js@^2.8.29:
+uglify-js@^2.8.29:
   version "2.8.29"
   resolved "https://registry.yarnpkg.com/uglify-js/-/uglify-js-2.8.29.tgz#29c5733148057bb4e1f75df35b7a9cb72e6a59dd"
   dependencies:
@@ -6788,6 +6782,13 @@ uglify-js@^2.6, uglify-js@^2.8.29:
   optionalDependencies:
     uglify-to-browserify "~1.0.0"
 
+uglify-js@^3.1.4:
+  version "3.6.0"
+  resolved "https://registry.yarnpkg.com/uglify-js/-/uglify-js-3.6.0.tgz#704681345c53a8b2079fb6cec294b05ead242ff5"
+  dependencies:
+    commander "~2.20.0"
+    source-map "~0.6.1"
+
 uglify-to-browserify@~1.0.0:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/uglify-to-browserify/-/uglify-to-browserify-1.0.2.tgz#6e0924d6bda6b5afe349e39a6d632850a0f882b7"