feat(exempt): add new options to exempt the milestones (#279)

* feat(exempt): add new options to exempt the milestones

closes #270

* test(milestones): add coverage

* test(issue): add coverage

* chore(rebase): fix all errors due to the rebase

also made some changes regarding the change I made with the lint scripts and prettier. I did not saw that some scripts were already here and I created to more to keep the old ones as well

* test(milestone): add coverage

* chore(index): update index

* fix(checks): remove checks over optional number options

the code was actually handling the case where the values are NaN so it's fine

src/classes/milestones.ts

@@ -0,0 +1,59 @@
+import deburr from 'lodash.deburr';
+import {wordsToList} from '../functions/words-to-list';
+import {IssueProcessorOptions} from '../IssueProcessor';
+import {Issue} from './issue';
+
+type CleanMilestone = string;
+
+export class Milestones {
+  private static _cleanMilestone(label: Readonly<string>): CleanMilestone {
+    return deburr(label.toLowerCase());
+  }
+
+  private readonly _options: IssueProcessorOptions;
+  private readonly _issue: Issue;
+
+  constructor(options: Readonly<IssueProcessorOptions>, issue: Issue) {
+    this._options = options;
+    this._issue = issue;
+  }
+
+  shouldExemptMilestones(): boolean {
+    const exemptMilestones: string[] = this._getExemptMilestones();
+
+    return exemptMilestones.some((exemptMilestone: Readonly<string>): boolean =>
+      this._hasMilestone(exemptMilestone)
+    );
+  }
+
+  private _getExemptMilestones(): string[] {
+    return wordsToList(
+      this._issue.isPullRequest
+        ? this._getExemptPullRequestMilestones()
+        : this._getExemptIssueMilestones()
+    );
+  }
+
+  private _getExemptIssueMilestones(): string {
+    return this._options.exemptIssueMilestones !== ''
+      ? this._options.exemptIssueMilestones
+      : this._options.exemptMilestones;
+  }
+
+  private _getExemptPullRequestMilestones(): string {
+    return this._options.exemptPrMilestones !== ''
+      ? this._options.exemptPrMilestones
+      : this._options.exemptMilestones;
+  }
+
+  private _hasMilestone(milestone: Readonly<string>): boolean {
+    if (!this._issue.milestone) {
+      return false;
+    }
+
+    return (
+      Milestones._cleanMilestone(milestone) ===
+      Milestones._cleanMilestone(this._issue.milestone.title)
+    );
+  }
+}