Vendor OCaml Migrate ParseTree.

Summary:
Problem: There exists reason packages in the wild that have `omp: *` as a
dependency. A new breaking change was released in omp 2.0.0. We cannot
compile against it. We also cannot upgrade to the intended replacement
for the old functionality we were using `ppxlib` because it doesn't
support older versions of omp.
The only solution is to vendor. This should unbreak existing libraries
that depend on older versions of Reason.
We should have had a constraint of `omp: < 2.0.0`, but even in that case
the package ecosystem essentially breaks because it splits into two
sides - ones that can use 2.0.0 omp and ones that cannot. Vendoring omp
solves that problem. It might not work during the next compiler upgrade
though (estimated six months).

Test Plan:

Reviewers:

CC:

HISTORY.md

@@ -1,11 +1,19 @@
 
-## 3.7.0
+## 3.6.1
+
 **New Feature, Non Breaking:**
-- Reason Syntax v4 [NEW-FEATURE-NON-BREAKING]: Angle Brackets Type Parameters (PARSING) (@jordwalke)[https://github.com/facebook/reason/pull/2604]
+- Reason Syntax v4 [NEW-FEATURE-NON-BREAKING]: Angle Brackets Type Parameters (PARSING) (@jordwalke)[#2604][https://github.com/facebook/reason/pull/2604]
 
 **Bug Fixes:**
 - Fix printing of externals that happen to have newlines/quotes in them (@jordwalke)[#2593](https://github.com/facebook/reason/pull/2593)
 - Fix parsing/printing of attributes on patterns (@jordwalke)[#2592](https://github.com/facebook/reason/pull/2592)
+- Fix Windows CI (@ManasJayanth) [#2611](https://github.com/facebook/reason/pull/2611)
+- Fix uncurry attribute on function application(@anmonteiro) [#2566](https://github.com/facebook/reason/pull/2566)
+- Support OCaml 4.11 (@anmonteiro) [#2582](https://github.com/facebook/reason/pull/2582)
+- Vendor ocaml-migrate-parsetree for greater compatibility (@jordwalke) [#2623](https://github.com/facebook/reason/pull/2623)
+
+**Docs:**
+- README Reason logo (@iamdarshshah)[#2609][https://github.com/facebook/reason/pull/2609]
 
 ## 3.6.0
 

esy.json

@@ -11,8 +11,8 @@
     "@opam/utop": " >= 1.17.0 < 2.5.0",
     "@opam/merlin-extend": " >= 0.6",
     "@opam/result": "*",
-    "@opam/ocaml-migrate-parsetree": " < 2.0.0",
-    "@opam/dune": "< 2.0.0"
+    "@opam/dune": "< 2.0.0",
+    "@opam/ppx_derivers": "< 2.0.0"
   },
   "devDependencies": {
     "@opam/merlin": "*",
@@ -69,7 +69,6 @@
         "@opam/menhir",
         "@opam/mmap",
         "@opam/ocplib-endian",
-        "@opam/ocaml-migrate-parsetree",
         "@opam/ocamlfind",
         "@opam/ppx_derivers",
         "@opam/react",