Fix link in alpha note and add link to OP ref from introduction

Author: breakanalysis

doc/modules/ROOT/pages/introduction.adoc

@@ -22,6 +22,8 @@ Each of these exist in one of three tiers of maturity:
 ** Indicates that the feature is experimental and might be changed or removed at any time.
 ** Features in this tier are prefixed with `gds.alpha.<operation>`.
 
+The xref:operations-reference/appendix-a.adoc[Operations Reference], lists all operations in GDS according to their tier.
+
 
 [[introduction-algorithms]]
 == Algorithms

doc/modules/ROOT/partials/operations-reference/alpha-note.adoc

@@ -1,4 +1,4 @@
 [.alpha-symbol]
 [.tier-note]
 This feature is in the alpha tier.
-For more information on feature tiers, see xref:operations-reference/appendix-a.adoc[Operations reference].
+For more information on feature tiers, see xref:introduction.adoc#introduction-tiers[API Tiers].