feat: Add markdown type in Mimes #14537

Job	Run time
Setup PHP Version for Code Coverage	3s
Others (8.3) / Sanity Tests	2m 51s
Others (8.4) / Sanity Tests	2m 40s
Others (8.5) / Sanity Tests	2m 47s
Others (8.2) / Sanity Tests	4m 57s
CacheLive (8.4) / Cache Live Tests	2m 16s
SeparateProcess (8.4) / tests	3m 50s
CacheLive (8.3) / Cache Live Tests	3m 4s
CacheLive (8.2) / Cache Live Tests	2m 42s
SeparateProcess (8.2) / tests	4m 3s
CacheLive (8.5) / Cache Live Tests	2m 28s
DatabaseLive (8.4, SQLSRV, 8.0) / tests	7m 0s
SeparateProcess (8.3) / tests	3m 31s
DatabaseLive (8.4, SQLite3, 8.0) / tests	2m 47s
SeparateProcess (8.5) / tests	3m 41s
DatabaseLive (8.3, OCI8, 8.0) / tests	6m 55s
DatabaseLive (8.2, MySQLi, 5.7) / tests	4m 47s
DatabaseLive (8.5, MySQLi, 8.0) / tests	5m 55s
DatabaseLive (8.5, Postgre, 8.0) / tests	2m 51s
DatabaseLive (8.4, OCI8, 8.0) / tests	7m 26s
DatabaseLive (8.5, SQLSRV, 8.0) / tests	5m 54s
DatabaseLive (8.3, SQLite3, 8.0) / tests	2m 25s
DatabaseLive (8.3, Postgre, 8.0) / tests	3m 1s
DatabaseLive (8.5, SQLite3, 8.0) / tests	2m 30s
DatabaseLive (8.3, SQLSRV, 8.0) / tests	5m 43s
DatabaseLive (8.2, SQLSRV, 8.0) / tests	7m 17s
DatabaseLive (8.2, SQLite3, 8.0) / tests	2m 54s
DatabaseLive (8.4, MySQLi, 8.0) / tests	4m 11s
DatabaseLive (8.3, MySQLi, 8.0) / tests	5m 20s
DatabaseLive (8.2, MySQLi, 8.0) / tests	5m 46s
DatabaseLive (8.5, OCI8, 8.0) / tests	8m 12s
DatabaseLive (8.2, Postgre, 8.0) / tests	3m 28s
DatabaseLive (8.2, OCI8, 8.0) / tests	8m 44s
DatabaseLive (8.4, Postgre, 8.0) / tests	3m 25s
Upload coverage results to Coveralls / coveralls	43s
	2h 26m 7s

Provide feedback