MdePkg: fix mdlint issues

Fix markdownlint formatting issues in README. Ignore `mipisyst`
markdownlint since it is a separate public repo outside of the edk2
ecosystem.

Signed-off-by: Sherry Fan <sherryfan@microsoft.com>

MdePkg/Library/MipiSysTLib/Readme.md

@@ -1,24 +1,32 @@
-## Introduction of MipiSysTLib ##
+# Introduction of MipiSysTLib #
+
 MipiSysTLib library is a upper level library consuming MIPI SYS-T submodule.
 It provides MIPI-related APIs in EDK2 format to be consumed.
 
 ## MipiSysTLib Version ##
+
 EDK2 supports building with v1.1+edk2 official version which was fully validated.
 
 ## HOW to Install MipiSysTLib for UEFI Building ##
+
 MIPI SYS-T repository was added as a submodule of EDK2 project. Please
 refer to edk2/Readme.md for how to clone the code.
 
 ## About GenMipiSystH.py ##
+
 "GenMipiSystH.py" is a Python script which is used for customizing the
 mipi_syst.h.in in mipi sys-T repository. The resulting file, mipi_syst.h, will
 be put to same folder level as this script.
-```
+
+```text
+
   mipisyst submodule                        MipiSysTLib library
 |---------------------| GenMipiSystH.py   |---------------------|
 |   mipi_syst.h.in    |-----------------> |   mipi_syst.h       |
 |---------------------|                   |---------------------|
+
 ```
+
 This script needs to be done once by a developer when adding some
 project-related definition or a new version of mipi_syst.h.in was released.
 Normal users do not need to do this, since the resulting file is stored

MdePkg/MdePkg.ci.yaml

@@ -110,14 +110,11 @@
         "AcceptableDependencies-HOST_APPLICATION":[
             "UnitTestFrameworkPkg/UnitTestFrameworkPkg.dec"
         ],
-        # For UEFI shell based apps
-        "AcceptableDependencies-UEFI_APPLICATION":[],
         "IgnoreInf": []
     },
 
     ## options defined ci/Plugin/DscCompleteCheck
     "DscCompleteCheck": {
-        "IgnoreInf": [""],
         "DscPath": "MdePkg.dsc"
     },
 
@@ -195,5 +192,11 @@
             "Library/BaseFdtLib/string.h",
             "mipi_syst.h"
         ]
+    },
+
+    ## options defined .pytool/Plugin/MarkdownLintCheck
+    "MarkdownLintCheck": {
+        "IgnoreFiles": [ "Library/MipiSysTLib/mipisyst"  # submodule outside of control
+        ]            # package root relative file, folder, or glob pattern to ignore
     }
 }