Meta: export getter/setter/method/constructor steps

Also adds some notes explaining that you might want to use "this" and "the given value" when defining them.

Author: tabatkins

index.bs

@@ -1793,14 +1793,18 @@ If an attribute has no <emu-t>static</emu-t> keyword, then it declares a
 it declares a [=static attribute=]. Note that in addition to being [=interface members=],
 [=read only=] [=regular attributes=] can be [=namespace members=] as well.
 
-The <dfn>getter steps</dfn> of an attribute |attr| should be introduced using text of the form “The
+The <dfn export>getter steps</dfn> of an attribute |attr| should be introduced using text of the form “The
 <code>|attr|</code> getter steps are:” followed by a list, or “The <code>|attr|</code> getter steps
 are to” followed by an inline description.
 
-The <dfn>setter steps</dfn> of an attribute |attr| should be introduced using text of the form “The
+The <dfn export>setter steps</dfn> of an attribute |attr| should be introduced using text of the form “The
 <code>|attr|</code> setter steps are:” followed by a list, or “The <code>|attr|</code> setter steps
 are to” followed by an inline description.
 
+Note: When defining [=getter steps=], you implicitly have access to [=this=].
+When defining [=setter steps=], you implicitly have access to [=this=] and
+[=the given value=].
+
 The [=identifier=] of an
 [=attribute=]
 must not be the same as the identifier
@@ -2347,11 +2351,13 @@ The following extended attributes are applicable to operations:
 [{{NewObject}}], and
 [{{SecureContext}}].
 
-The <dfn>method steps</dfn> of an operation |operation| should be introduced using text of the form
+The <dfn export>method steps</dfn> of an operation |operation| should be introduced using text of the form
 “The <code>|operation|(<var ignore>arg1</var>, <var ignore>arg2</var>, ...)</code> method
 steps are:” followed by a list, or “The <code>|operation|(<var ignore>arg1</var>,
 <var ignore>arg2</var>, ...)</code> method steps are to” followed by an inline description.
 
+Note: When defining [=method steps=], you implicitly have access to [=this=].
+
 <pre class="grammar" id="prod-DefaultValue">
     DefaultValue :
         ConstValue
@@ -2555,7 +2561,7 @@ Multiple [=constructor operations=] may appear on a given [=interface=].
 For each [=constructor operation=] on the [=interface=], there will be a way to attempt to
 construct an instance by passing the specified arguments.
 
-The <dfn>constructor steps</dfn> of a [=constructor operation=] that is a member of an interface
+The <dfn export>constructor steps</dfn> of a [=constructor operation=] that is a member of an interface
 named |interface| should be introduced using text of the form “The
 <code>new |interface|(<var ignore>arg1</var>, <var ignore>arg2</var>, ...)</code> constructor steps
 are:” followed by a list, or “The