Lagom: Add fuzz testing for LibJS using libFuzzer (#1692)

Note: clang only (see https://llvm.org/docs/LibFuzzer.html)

- add FuzzJs which will run the LibJS parser on random javascript inputs
- added a basic dictionary of javascript tokens

To use fuzzer:
CC=/usr/bin/clang CXX=/usr/bin/clang++ cmake -DENABLE_FUZZER_SANITIZER=1 ..
Fuzzers/FuzzJs -dict=../Fuzzers/FuzzJs.dict

Meta/Lagom/Fuzzers/CMakeLists.txt

@@ -0,0 +1,9 @@
+add_executable(FuzzJs FuzzJs.cpp)
+target_compile_options(FuzzJs
+    PRIVATE $<$<C_COMPILER_ID:Clang>:-g -O1 -fsanitize=fuzzer>
+    )
+
+target_link_libraries(FuzzJs
+    PUBLIC lagom
+    PRIVATE $<$<C_COMPILER_ID:Clang>:-fsanitize=fuzzer>
+    )