doc: Adopters list in README (#252)

Adds a list of most popular projects using avo, based on Github Stars.

Auto-generated from the third-party packages list using docgen.

Updates #101

tests/thirdparty/config.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"path"
 	"path/filepath"
+	"sort"
 	"strings"
 )
 
@@ -22,6 +23,11 @@ func (r GithubRepository) String() string {
 	return path.Join(r.Owner, r.Name)
 }
 
+// URL returns the Github repository URL.
+func (r GithubRepository) URL() string {
+	return fmt.Sprintf("https://github.com/%s", r)
+}
+
 // CloneURL returns the git clone URL.
 func (r GithubRepository) CloneURL() string {
 	return fmt.Sprintf("https://github.com/%s.git", r)
@@ -256,6 +262,25 @@ func (p Packages) Validate() error {
 	return nil
 }
 
+// Ranked returns a copy of the packages list ranked in desending order of
+// popularity.
+func (p Packages) Ranked() Packages {
+	ranked := append(Packages(nil), p...)
+	sort.SliceStable(ranked, func(i, j int) bool {
+		return ranked[i].Metadata.Stars > ranked[j].Metadata.Stars
+	})
+	return ranked
+}
+
+// Top returns the top n most popular packages.
+func (p Packages) Top(n int) Packages {
+	top := p.Ranked()
+	if len(top) > n {
+		top = top[:n]
+	}
+	return top
+}
+
 // LoadPackages loads a list of package configurations from JSON format.
 func LoadPackages(r io.Reader) (Packages, error) {
 	var pkgs Packages