Update README.md

Author: Orta Therox

README.md

@@ -72,7 +72,7 @@ To give you a sense of whether we will accept changes, you can use these heurist
 
 - Does the new objects or fields show up in [mdn/browser-compat-data](https://github.com/mdn/browser-compat-data)? If not, it's likely too soon.
 - Is the IDL source from WHATWG?
-    - Are the additions available in at least two of Firefox, Safari and Chromium?
+    - Are the additions available in at least two of [Firefox](https://searchfox.org/mozilla-central/search?q=&path=), [Safari](https://webkit-search.igalia.com/webkit/search?q=&path=) and Chromium?
 - Is the IDL source from W3C?
     - What stage of the [W3C process](https://en.wikipedia.org/wiki/World_Wide_Web_Consortium#Specification_maturation) is the proposal for these changes: We aim for Proposed recommendation, but can accept Candidate recommendation for stable looking proposals.
     - If it's at Working draft the additions available in all three of Firefox, Safari and Chromium
@@ -103,4 +103,4 @@ To give you a sense of whether we will accept changes, you can use these heurist
 - `overridingTypes.json`: types that are defined in the spec file but has a better or more up-to-date definitions in the json files.
 - `removedTypes.json`: types that are defined in the spec file but should be removed.
 - `comments.json`: comment strings to be embedded in the generated .js files.
-- `deprecatedMessage.json`: the reason why one type is deprecated. The reason why it is a separate file rather than merge in comment.json is mdn/apiDescriptions.json would also possibly be deprecated.
+- `deprecatedMessage.json`: the reason why one type is deprecated. The reason why it is a separate file rather than merge in comment.json is mdn/apiDescriptions.json would also possibly be deprecated.