Add October Matins readings for SanctiM-track saints

9 of October's 13 SanctiM-track saints authored. Found a new wrinkle:
St. Justina and St. Gall are genuinely Monastic-only (no Tridentine
file at all) but their own SanctiM files turn out to be Common-only
with no proper Lectio content -- being Monastic-only doesn't guarantee
real text to transcribe.

src/data/propers/nocturn-readings/st-marcus.yml

@@ -0,0 +1,30 @@
+# Matins Nocturn 2 reading for St. Marcus, Pope, Confessor (Oct 7). No
+# genuine SanctiM match: the correct Tridentine file is the suffixed
+# `Sancti/10-07t.txt` (the plain `Sancti/10-07.txt` has no proper
+# content of its own, and `Sancti/10-07cc.txt` is Ss. Sergius, Bacchus,
+# Marcellus, and Apuleius instead), and the only SanctiM files for
+# this date base `@Sancti/10-07` (the plain, contentless file) or are
+# unrelated own content — a missed pre-1955-pool candidate rather
+# than a genuine SanctiM case (see memory vu-matins-pre1955-saints,
+# vu-matins-sanctim-saints).
+# web/www/horas/Latin/Sancti/10-07t.txt, English/Sancti/10-07t.txt.
+# Single lesson (simplex-feast Lectio93), one continuous account, no
+# responsory given in the source.
+id: st-marcus
+readings:
+  - nocturn: 2
+    isGospel: false
+    text:
+      la: >-
+        Marcus, Romanus, Constantino Magno imperatóre Pontifex, instituit ut epíscopus
+        Ostiénsis, a quo Romanus Pontifex consecrátur, pallio uterétur. Duas Romæ basilicas
+        ædificávit, álteram in Urbe, álteram via Ardeatina; quas Constantinus, auctas, magnis
+        munéribus exornávit. Vixit in pontificatu menses octo, sepultúsque est in cœmeterio
+        Balbinæ.
+      en: >-
+        This Mark was a Roman, who sat as Pope in the reign of the Emperor Constantine the
+        Great. He ordained that the Bishop of Ostia, by whom the Bishop of Rome is consecrated,
+        should use the Pallium. He built two Churches, one in the city and the other on the
+        Ardeatine Way, which Constantine enlarged and richly gifted. Mark lived as Pope eight
+        months, and was buried in the Cemetery of Balbina.
+    status: { la: verified, en: verified }