Add WebGPU Shading Language lexer (#776)

https://w3.org/TR/WGSL

Generated from the Pygments lexer I wrote, in
pygments/pygments#2386

lexers/testdata/wgsl.attribute.actual

@@ -0,0 +1,5 @@
+@id(0) override x:i32 = 1;
+@ id(1) override y:i32 = 2;
+@//comment
+id(1) override z:i32 = 3;
+@must_use fn foo() -> i32 { return 32; }

lexers/testdata/wgsl.attribute.expected

@@ -0,0 +1,74 @@
+[
+  {"type":"NameDecorator","value":"@id"},
+  {"type":"Punctuation","value":"("},
+  {"type":"LiteralNumberInteger","value":"0"},
+  {"type":"Punctuation","value":")"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"KeywordDeclaration","value":"override"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Name","value":"x"},
+  {"type":"Punctuation","value":":"},
+  {"type":"NameBuiltin","value":"i32"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Operator","value":"="},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"LiteralNumberInteger","value":"1"},
+  {"type":"Punctuation","value":";"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"NameDecorator","value":"@"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameDecorator","value":"id"},
+  {"type":"Punctuation","value":"("},
+  {"type":"LiteralNumberInteger","value":"1"},
+  {"type":"Punctuation","value":")"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"KeywordDeclaration","value":"override"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Name","value":"y"},
+  {"type":"Punctuation","value":":"},
+  {"type":"NameBuiltin","value":"i32"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Operator","value":"="},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"LiteralNumberInteger","value":"2"},
+  {"type":"Punctuation","value":";"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"NameDecorator","value":"@"},
+  {"type":"CommentSingle","value":"//comment\n"},
+  {"type":"NameDecorator","value":"id"},
+  {"type":"Punctuation","value":"("},
+  {"type":"LiteralNumberInteger","value":"1"},
+  {"type":"Punctuation","value":")"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"KeywordDeclaration","value":"override"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Name","value":"z"},
+  {"type":"Punctuation","value":":"},
+  {"type":"NameBuiltin","value":"i32"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Operator","value":"="},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"LiteralNumberInteger","value":"3"},
+  {"type":"Punctuation","value":";"},
+  {"type":"TextWhitespace","value":"\n"},
+  {"type":"NameDecorator","value":"@must_use"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"fn"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Name","value":"foo"},
+  {"type":"Punctuation","value":"()"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Punctuation","value":"-\u003e"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"NameBuiltin","value":"i32"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Punctuation","value":"{"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Keyword","value":"return"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"LiteralNumberInteger","value":"32"},
+  {"type":"Punctuation","value":";"},
+  {"type":"TextWhitespace","value":" "},
+  {"type":"Punctuation","value":"}"},
+  {"type":"TextWhitespace","value":"\n"}
+]

lexers/testdata/wgsl.block.comment.actual

@@ -0,0 +1,8 @@
+ /**/
+ /*block with newline
+  */
+ /*block with line
+ ending comment//  */
+ /* nested /*
+  */
+  */

lexers/testdata/wgsl.block.comment.expected

@@ -0,0 +1,11 @@
+[
+  {"type":"TextWhitespace","value":" "},
+  {"type":"CommentMultiline","value":"/**/"},
+  {"type":"TextWhitespace","value":"\n "},
+  {"type":"CommentMultiline","value":"/*block with newline\n  */"},
+  {"type":"TextWhitespace","value":"\n "},
+  {"type":"CommentMultiline","value":"/*block with line\n ending comment//  */"},
+  {"type":"TextWhitespace","value":"\n "},
+  {"type":"CommentMultiline","value":"/* nested /*\n  */\n  */"},
+  {"type":"TextWhitespace","value":"\n"}
+]

lexers/testdata/wgsl.const.numbers.actual

@@ -0,0 +1,50 @@
+const a = 0;
+const au = 0u;
+const ai = 0i;
+const b = 12345;
+const bu = 12345u;
+const bi= 12345i;
+const c = 0x0;
+const cu = 0x0u;
+const ci = 0x0i;
+const d = 0x12345;
+const di = 0x12345i;
+const du = 0x12345u;
+const eh = 0h;
+const ef = 0f;
+const f = 1.;
+const fh = 1.h;
+const ff = 1.f;
+const g = .1;
+const gh = .1h;
+const gf = .1f;
+const g = 1e1;
+const gh = 1e1h;
+const gf = 1e1f;
+const h = 1e+1;
+const hh = 1e+1h;
+const hf = 1e+1f;
+const i = 1e-1;
+const ih = 1e-1h;
+const if = 1e-1f;
+const j = 1.0e+1;
+const jh = 1.0e+1h;
+const jf= 1.0e+1f;
+const k = 1.0e-1;
+const kh = 1.0e-1h;
+const kf= 1.0e-1f;
+const l = 0x1p1;
+const lh = 0x1p1h;
+const lf = 0x1p1f;
+const m = 0x1p+1;
+const mh = 0x1p+1h;
+const mf = 0x1p+1f;
+const n = 0x1p-1;
+const nh = 0x1p-1h;
+const nf = 0x1p-1f;
+const o = 0x1.p1;
+const oh = 0x1.p1h;
+const of = 0x1.p1f;
+const p = 0x.1p1;
+const ph = 0x.1p1h;
+const pf = 0x.1p1f;