Correct spelling mistakes (#1703)

* Nitpicking

options/locale/locale_en-US.ini

@@ -839,7 +839,7 @@ settings.githook_edit_desc = If the hook is inactive, sample content will be pre
 settings.githook_name = Hook Name
 settings.githook_content = Hook Content
 settings.update_githook = Update Hook
-settings.add_webhook_desc = Gitea will send a <code>POST</code> request to the URL you specify, along with regarding the event that occured. You can also specify what kind of data format you'd like to get upon triggering the hook (JSON, x-www-form-urlencoded, XML, etc). More information can be found in our <a target="_blank" rel="noopener" href="%s">Webhooks Guide</a>.
+settings.add_webhook_desc = Gitea will send a <code>POST</code> request to the URL you specify, along with regarding the event that occurred. You can also specify what kind of data format you'd like to get upon triggering the hook (JSON, x-www-form-urlencoded, XML, etc). More information can be found in our <a target="_blank" rel="noopener" href="%s">Webhooks Guide</a>.
 settings.payload_url = Payload URL
 settings.content_type = Content Type
 settings.secret = Secret
@@ -899,7 +899,7 @@ settings.no_protected_branch = There are no protected branches
 diff.browse_source = Browse Source
 diff.parent = parent
 diff.commit = commit
-diff.data_not_available = Diff Content Not Availaible
+diff.data_not_available = Diff Content Not Available
 diff.show_diff_stats = Show Diff Stats
 diff.show_split_view = Split View
 diff.show_unified_view = Unified View
@@ -1279,7 +1279,7 @@ config.mailer_name = Name
 config.mailer_host = Host
 config.mailer_user = User
 config.send_test_mail = Send Test Email
-config.test_mail_failed = Fail to send test email to '%s': %v
+config.test_mail_failed = Failed to send test email to '%s': %v
 config.test_mail_sent = Test email has been sent to '%s'.
 
 config.oauth_config = OAuth Configuration
@@ -1332,7 +1332,7 @@ monitor.start = Start Time
 monitor.execute_time = Execution Time
 
 notices.system_notice_list = System Notices
-notices.view_detail_header = View Notice Detail
+notices.view_detail_header = View Notice Details
 notices.actions = Actions
 notices.select_all = Select All
 notices.deselect_all = Deselect All
@@ -1398,11 +1398,10 @@ pin = Pin notification
 mark_as_read = Mark as read
 mark_as_unread = Mark as unread
 
-
 [gpg]
 error.extract_sign = Failed to extract signature
 error.generate_hash = Failed to generate hash of commit
 error.no_committer_account = No account linked to committer email
 error.no_gpg_keys_found = "No known key found for this signature in database"
 error.not_signed_commit = "Not a signed commit"
-error.failed_retrieval_gpg_keys = "Failed to retrieve any key attached to the commiter account"
+error.failed_retrieval_gpg_keys = "Failed to retrieve any key attached to the committer account"