Fix Syntax hightlighting for manifest XML files

[JimSuplizio]

What does this PR do?

When I'd made the changes to create the "language" for limiting when certain manifest commands are available I'd inadvertently caused the manifest xml files to lose syntax highlighting. This change adds the correct grammar and syntax files to the package.json. The language file is just a pass through as there's nothing special about the syntax for the manifest XML at this time.

What issues does this PR fix or reference?

@W-5698186@

[codecov]

Codecov Report

Merging #823 into develop will increase coverage by 0.16%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #823      +/-   ##
===========================================
+ Coverage    73.11%   73.27%   +0.16%     
===========================================
  Files          168      168              
  Lines         6814     6814              
  Branches      1076     1076              
===========================================
+ Hits          4982     4993      +11     
+ Misses        1559     1549      -10     
+ Partials       273      272       -1

Impacted Files	Coverage Δ
...x-replay-debugger/test/integration/goldFileUtil.ts	95.65% <0%> (+23.91%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update caad905...8a0c218. Read the comment docs.