message: Properly close subscript tags
diff: @@ -7,7 +7,7 @@ description language. This how most users will interact with data descriptions.
  ### Whitespace and comments
  -> <sub>Grammar:<sub>
  +> <sub>Grammar:</sub>
  >
  > _horizontal-tab_ ::=\
  > &emsp;|&ensp;U+0009
  @@ -67,7 +67,7 @@ description language. This how most users will interact with data descriptions.
  ### Keywords and identifiers
  -> <sub>Grammar:<sub>
  +> <sub>Grammar:</sub>
  >
  > _keyword_ ::=\
  > &emsp;|&ensp; `struct`
  @@ -80,7 +80,7 @@ description language. This how most users will interact with data descriptions.
  ### Punctuation
  -> <sub>Grammar:<sub>
  +> <sub>Grammar:</sub>
  >
  > _punctuation_ ::=\
  > &emsp;|&ensp;`{`\
  @@ -90,7 +90,7 @@ description language. This how most users will interact with data descriptions.
  ### Tokens
  -> <sub>Grammar:<sub>
  +> <sub>Grammar:</sub>
  >
  > _token_ ::=\
  > &emsp;|&ensp;_white-space_\
  @@ -106,7 +106,7 @@ process.
  ### Terms
  -> <sub>Grammar:<sub>
  +> <sub>Grammar:</sub>
  >
  > _term_ ::=\
  > &emsp;|&ensp;_ident_
  @@ -129,7 +129,7 @@ struct Point3 {
  Structures are composite types that are have a name and a list of fields. The
  fields within a structure must have unique names.
  -> <sub>Grammar:<sub>
  +> <sub>Grammar:</sub>
  >
  > _struct-type-field_ ::=\
  > &emsp;|&ensp;_doc-comment_<sup>?</sup> _ident_ `:` _term_
  @@ -144,7 +144,7 @@ fields within a structure must have unique names.
  Modules are lists of zero-or-more definitions. Definitions within a module must have unique names.
  -> <sub>Grammar:<sub>
  +> <sub>Grammar:</sub>
  >
  > _item_ ::=\
  > &emsp;|&ensp;_struct-type-definition_
  