Update MD049/emphasis-style and MD050/strong-style to not report intraword asterisks/underscores as violations because exchanging either alters meaning (fixes #789).

test/snapshots/markdownlint-test-scenarios.js.md

@@ -10754,7 +10754,12 @@ Generated by [AVA](https://avajs.dev).
       ␊
       This is *not* {MD049}␊
       ␊
+      Internal emphasis is preserved:␊
+      apple*banana*cherry, apple*banana*, *banana*cherry␊
+      apple_banana_cherry, apple_banana_, _banana_cherry␊
+      ␊
       <!-- markdownlint-configure-file {␊
+        "MD037": false,␊
         "MD049": {␊
           "style": "asterisk"␊
         }␊
@@ -10815,7 +10820,12 @@ Generated by [AVA](https://avajs.dev).
       ␊
       This is _not_ {MD049}␊
       ␊
+      Internal emphasis is preserved:␊
+      apple*banana*cherry, apple*banana*, *banana*cherry␊
+      apple_banana_cherry, apple_banana_, _banana_cherry␊
+      ␊
       <!-- markdownlint-configure-file {␊
+        "MD037": false,␊
         "MD049": {␊
           "style": "underscore"␊
         }␊
@@ -44028,6 +44038,10 @@ Generated by [AVA](https://avajs.dev).
       ␊
       This is **not** {MD050}␊
       ␊
+      Internal emphasis is preserved:␊
+      apple**banana**cherry, apple**banana**, **banana**cherry␊
+      apple__banana__cherry, apple__banana__, __banana__cherry␊
+      ␊
       <!-- markdownlint-configure-file {␊
         "MD050": {␊
           "style": "asterisk"␊
@@ -44089,6 +44103,10 @@ Generated by [AVA](https://avajs.dev).
       ␊
       This is __not__ {MD050}␊
       ␊
+      Internal emphasis is preserved:␊
+      apple**banana**cherry, apple**banana**, **banana**cherry␊
+      apple__banana__cherry, apple__banana__, __banana__cherry␊
+      ␊
       <!-- markdownlint-configure-file {␊
         "MD050": {␊
           "style": "underscore"␊