fonts: Add KaTeX custom fonts

Downloaded from:
  https://github.com/KaTeX/KaTeX/tree/2fe1941b7/fonts

These fonts will be used in later commits to show KaTeX content.

Author: rajveermalviya

assets/KaTeX/KaTeX_AMS-Regular.ttf

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2013-2020 Khan Academy and other contributors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

assets/KaTeX/KaTeX_Caligraphic-Bold.ttf

@@ -12,6 +12,9 @@ import 'package:flutter/services.dart';
 Stream<LicenseEntry> additionalLicenses() async* {
   // Alphabetic by path.
 
+  yield LicenseEntryWithLineBreaks(
+    ['KaTeX'],
+    await rootBundle.loadString('assets/KaTeX/LICENSE'));
   yield LicenseEntryWithLineBreaks(
     ['Noto Color Emoji'],
     await rootBundle.loadString('assets/Noto_Color_Emoji/LICENSE'));

assets/KaTeX/KaTeX_Caligraphic-Regular.ttf

@@ -122,6 +122,74 @@ flutter:
     - assets/Source_Sans_3/LICENSE.md
 
   fonts:
+    # KaTeX's custom fonts.
+    - family: KaTeX_AMS
+      fonts:
+        - asset: assets/KaTeX/KaTeX_AMS-Regular.ttf
+
+    - family: KaTeX_Caligraphic
+      fonts:
+        - asset: assets/KaTeX/KaTeX_Caligraphic-Regular.ttf
+        - asset: assets/KaTeX/KaTeX_Caligraphic-Bold.ttf
+          weight: 700
+
+    - family: KaTeX_Fraktur
+      fonts:
+        - asset: assets/KaTeX/KaTeX_Fraktur-Regular.ttf
+        - asset: assets/KaTeX/KaTeX_Fraktur-Bold.ttf
+          weight: 700
+
+    - family: KaTeX_Main
+      fonts:
+        - asset: assets/KaTeX/KaTeX_Main-Regular.ttf
+        - asset: assets/KaTeX/KaTeX_Main-Bold.ttf
+          weight: 700
+        - asset: assets/KaTeX/KaTeX_Main-Italic.ttf
+          style: italic
+        - asset: assets/KaTeX/KaTeX_Main-BoldItalic.ttf
+          weight: 700
+          style: italic
+
+    - family: KaTeX_Math
+      fonts:
+        - asset: assets/KaTeX/KaTeX_Math-Italic.ttf
+          style: italic
+        - asset: assets/KaTeX/KaTeX_Math-BoldItalic.ttf
+          weight: 700
+          style: italic
+
+    - family: KaTeX_SansSerif
+      fonts:
+        - asset: assets/KaTeX/KaTeX_SansSerif-Regular.ttf
+        - asset: assets/KaTeX/KaTeX_SansSerif-Bold.ttf
+          weight: 700
+        - asset: assets/KaTeX/KaTeX_SansSerif-Italic.ttf
+          style: italic
+
+    - family: KaTeX_Script
+      fonts:
+        - asset: assets/KaTeX/KaTeX_Script-Regular.ttf
+
+    - family: KaTeX_Size1
+      fonts:
+        - asset: assets/KaTeX/KaTeX_Size1-Regular.ttf
+
+    - family: KaTeX_Size2
+      fonts:
+        - asset: assets/KaTeX/KaTeX_Size2-Regular.ttf
+
+    - family: KaTeX_Size3
+      fonts:
+        - asset: assets/KaTeX/KaTeX_Size3-Regular.ttf
+
+    - family: KaTeX_Size4
+      fonts:
+        - asset: assets/KaTeX/KaTeX_Size4-Regular.ttf
+
+    - family: KaTeX_Typewriter
+      fonts:
+        - asset: assets/KaTeX/KaTeX_Typewriter-Regular.ttf
+
     # Google's emoji font. (Web uses these emoji for the "Google" emojiset.)
     #
     # This should not be used on iOS.