[vcpkg manifest] Add documentation! (#13488)

* [vcpkg docs] add docs for manifest files

These are just for the maintainer docs,
not user docs.

* [vcpkg] EBNF-ify platform expression parsing

this modifies nothing about what strings are accepted or rejected,
it just moves stuff around.

also adds tests.

* [vcpkg docs] add manifest mode example

* [wip] docs for augustin

also fix tabs

* [vcpkg manifest] switch to using maps for features

* Apply suggestions from code review

* un-experimentize format-manifest

* flesh out the user manifest mode docs

* CRs

* billy CRs

* final personal pass-thru

1 files changed, 1 insertions, 1 deletions

diff --git a/toolsrc/src/vcpkg-test/manifests.cpp b/toolsrc/src/vcpkg-test/manifests.cpp
index 9a0ca94e2..0d5c9782a 100644
--- a/toolsrc/src/vcpkg-test/manifests.cpp
+++ b/toolsrc/src/vcpkg-test/manifests.cpp
@@ -250,7 +250,7 @@ TEST_CASE ("SourceParagraph manifest empty supports", "[manifests]")
 
 TEST_CASE ("Serialize all the ports", "[manifests]")
 {
-    std::vector<std::string> args_list = {"x-format-manifest"};
+    std::vector<std::string> args_list = {"format-manifest"};
     auto& fs = Files::get_real_filesystem();
     auto args = VcpkgCmdArguments::create_from_arg_sequence(args_list.data(), args_list.data() + args_list.size());
     VcpkgPaths paths{fs, args};