doc: fix some errors in esm resolution algorithms

doc/api/esm.md

@@ -937,7 +937,7 @@ The resolver can throw the following errors:
 >       2. If _resolved_ is not **null** or **undefined**, return _resolved_.
 > 3. Otherwise, if _exports_ is an Object and all keys of _exports_ start with
 >    _"."_, then
->    1. Let _matchKey_ be the string _"./"_ concatenated with _subpath_.
+>    1. Let _matchKey_ be _subpath_ (by this point, it should be prefixed with _"./"_).
 >    2. Let _resolved_ be the result of **PACKAGE\_IMPORTS\_EXPORTS\_RESOLVE**(
 >       _matchKey_, _exports_, _packageURL_, **false**, _conditions_).
 >    3. If _resolved_ is not **null** or **undefined**, return _resolved_.
@@ -1019,7 +1019,7 @@ _isImports_, _conditions_)
 >       Package Target_ error.
 >    3. Let _resolvedTarget_ be the URL resolution of the concatenation of
 >       _packageURL_ and _target_.
->    4. Assert: _resolvedTarget_ is contained in _packageURL_.
+>    4. Assert: _packageURL_ is contained in _resolvedTarget_.
 >    5. If _patternMatch_ is **null**, then
 >       1. Return _resolvedTarget_.
 >    6. If _patternMatch_ split on _"/"_ or _"\\"_ contains any _""_, _"."_,