Some improvements

- Use classes
- Split buildx/builder modules
- Additional tests

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

src/docker.ts

@@ -1,19 +1,21 @@
 import * as exec from '@actions/exec';
 
-export async function isAvailable(): Promise<boolean> {
-  return await exec
-    .getExecOutput('docker', undefined, {
-      ignoreReturnCode: true,
-      silent: true
-    })
-    .then(res => {
-      if (res.stderr.length > 0 && res.exitCode != 0) {
+export class Docker {
+  public static async isAvailable(): Promise<boolean> {
+    return await exec
+      .getExecOutput('docker', undefined, {
+        ignoreReturnCode: true,
+        silent: true
+      })
+      .then(res => {
+        if (res.stderr.length > 0 && res.exitCode != 0) {
+          return false;
+        }
+        return res.exitCode == 0;
+      })
+      // eslint-disable-next-line @typescript-eslint/no-unused-vars
+      .catch(error => {
         return false;
-      }
-      return res.exitCode == 0;
-    })
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    .catch(error => {
-      return false;
-    });
+      });
+  }
 }