Specs and Docs: minor updates to fix mistakes I found when proof-reading

sky/specs/parsing.md

 Parsing
 =======
 
 Parsing in Sky is a strict pipeline consisting of five stages:
 
 - decoding, which converts incoming bytes into Unicode characters
   using UTF-8.
 
 - normalising, which manipulates the sequence of characters.
 
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 If the token is a start tag token, notify the JavaScript token stream
 callback of the token.
 
 Then, pass the tokens to the tree construction stage.
 
 
 Tree construction stage
 -----------------------
 
 To construct a node tree from a _sequence of tokens_ and a document
-_document_:
+_document_ (this is implemented in JS):
 
 1. Initialize the _stack of open nodes_ to be _document_.
 2. Initialize _imported modules_ to an empty list.
 3. Consider each token _token_ in the _sequence of tokens_ in turn, as
    follows. If a token is to be skipped, then jump straight to the
    next token, without doing any more work with the skipped token.
    - If _token_ is a string token,
      1. If the value of the token contains only U+0020 and U+000A
         characters, and there is no ``t`` element on the _stack of
         open nodes_, then skip the token.
@@ skipping 38 matching lines @@
         popped.
      5. If _node_'s tag name is ``script``, then yield until _imported
         modules_ contains no entries with unresolved promises, then
         execute the script given by the element's contents, using the
         associated names as appropriate.
    - If _token_ is an automatic end tag token:
      1. Pop the top node from the _stack of open nodes_, unless it is
         the document.
 4. Yield until _imported modules_ has no promises.
 5. Fire a ``load`` event at the _parsing context_ object.