test: add manual embedded strings test

Author: nkrkv

test/highlight/embedded.res

@@ -0,0 +1,15 @@
+// NOT AN AUTOMATED TEST.
+//
+// Looks like Tree-sitter test framework does not allow to test
+// for correct language embedding. So, this file is just a showcase
+// to observe results with eyes.
+//
+// You should see comprehensive highlighting for constructs inside
+// strings. That is, they should not look like plain strings if
+// you have corresponding grammar installed.
+
+// :TSInstall javascript
+let inc = %raw(`function(x) {return x + 1;}`)
+
+// :TSInstall graphql
+let gql = %graphql(`{ hero { name } }`)