add some related articles

Author: danrusei

numbers/README.md

@@ -1 +1,10 @@
-#TBD
+# Numbers
+
+Articles about numbers in Go:
+
+* [Understanding Data Types in Go](https://www.digitalocean.com/community/tutorials/understanding-data-types-in-go)
+
+## Related Go packages
+
+* Math [pkg.go.dev](https://pkg.go.dev/math@go1.15.6)
+* Strconv [pkg.go.dev](https://pkg.go.dev/strconv@go1.15.6)

strings/README.md

@@ -1 +1,12 @@
-#TBD
+# Go Strings and Slices
+
+Articles about Go slices and strings:
+
+* [Go Slices: usage and internals](https://blog.golang.org/slices-intro)
+* [Arrays, slices (and strings): The mechanics of 'append'](https://blog.golang.org/slices)
+* [Strings, bytes, runes and characters in Go](https://blog.golang.org/strings)
+
+## Related Go packages
+
+* Strings - [pkg.go.dev](https://pkg.go.dev/strings)
+* Bytes - [pkg.go.dev](https://pkg.go.dev/bytes)