Add draft text/wgsl media type registration. WGSL uses UTF-8

Fixes: gpuweb#1682 gpuweb#565

wgsl/index.bs

@@ -437,12 +437,7 @@ The WebGPU specification describes the consequences of each kind of error.
 
 # Textual Structure # {#textual-structure}
 
-A WGSL program is text.
-This specification does not prescribe a particular encoding for that text.
-However, UTF-8 is always a valid encoding for a WGSL program.
-
-Note: The intent of promoting UTF-8 like this is to simplify interchange of WGSL programs
-and to encourage interoperability among tools.
+A WGSL program is Unicode text using the UTF-8 encoding.
 
 WGSL program text consists of a sequence of Unicode [=code points=], grouped into contiguous non-empty sets forming:
 * [=comments=]

wgsl/media-type-registration.txt

@@ -0,0 +1,65 @@
+Type name: text
+
+Subtype name: wgsl
+
+Required parameters: N/A
+
+Optional parameters: None
+
+Encoding considerations: binary
+
+  WGSL is Unicode text using the UTF-8 encoding. See [WGSL] Section
+  3. Textual Structure.
+
+Security considerations:
+
+  WebGPU Shading Language (WGSL) is a programming language for GPU
+  code to be executed in the context of the WebGPU API. For security
+  considerations, see [WebGPU] Section 2.1 Security Considerations.
+
+Interoperability considerations:
+
+  Implementations of WebGPU may have different capabilities, and
+  these differences may affect what features may be exercised by
+  WGSL programs. See [WebGPU] Section 3.6 Optional capabilities,
+  and [WGSL] Section 11. Language Extensions.
+
+  It is expected that implementations will behave as if this
+  registration applies to later editions of [WGSL], and its published
+  specification references may be updated accordingly from time to
+  time.  Although this expectation is unusual among media type
+  registrations, it matches widespread industry conventions.
+
+Published specification: [WGSL]
+
+Applications that use this media type:
+
+  Implementations of WebGPU [WebGPU]. This is expected to include
+  web browsers.
+
+Fragment identifier considerations: None
+
+Additional information:
+
+  Magic number(s): None
+  File extension(s): .wgsl
+  Macintosh file type code(s): TEXT
+
+Person & email address to contact for further information:
+  David Neto, dneto@google.com, or  the Editors listed in [WGSL]. 
+
+Intended usage:  COMMON
+
+Author:  W3C.  See the Editors listed in [WGSL].
+
+Change controller:  W3C
+
+Normative References:
+
+  [WebGPU] W3C, "WebGPU” W3C Working Draft, October 2022.
+      <https://www.w3.org/TR/webgpu/>.
+
+  [WGSL] W3C, “WebGPU Shading Language” W3C Working Draft, October
+      2022.  <https://www.w3.org/TR/wgsl/>.
+
+