Screenshot metadata dialog (#490)

* docs: Add json schema for screenshot metadata

* feat(.NET): Add function to open a file and read screenshot metadata to AppApi

* refactor(.NET): Check initial file dialog directory before set

Paranoia is fun

* refactor(.NET): Stop reading entire png files into memory to check 8 bytes

* refactor(.NET): Handle endianness and keyword encoding correctly for screenshots

* docs: Add xmldocs and some comments to parts of the screenshot helper

* screenshot metadata dialog

* screenshot metadata dialog 1

* fix: file dialog open bool not resetting properly

* screenshot metadata dialog 2

* fix: Stop png parser from dying on bad files

Parser would keep reading past a file's IEND chunk, and it finally found one that had junk data past IEND. It died. This fixes that.

It also encapsulates the Read function in a try/catch so VRCX doesn't crash if it fails due to a corrupted file.

* fix: buggy carousel transition animation

---------

Co-authored-by: Teacup <git@teadev.xyz>

html/src/localization/strings/en.json

@@ -348,6 +348,7 @@
                 "advanced": {
                     "header": "Advanced",
                     "launch_options": "Launch Options",
+                    "screenshot_metadata": "Screenshot Metadata",
                     "pending_offline": {
                         "header": "Pending Offline",
                         "description": "Delay before marking user as offline (fixes false positives)",
@@ -1051,6 +1052,10 @@
             "password_placeholder": "Input new password",
             "re_input_placeholder": "Re-input password",
             "ok": "OK"
+        },
+        "screenshot_metadata": {
+            "header": "Screenshot Metadata",
+            "browse": "Browse"
         }
     },
     "prompt": {