Styled the src/extensions README

.gitignore

@@ -23,7 +23,7 @@ Thumbs.db
 # ignore everything in the dev extension directory EXCEPT the README
 # (so that the directory is non-empty and can be in git)
 /src/extensions/dev/*
-!/src/extensions/dev/README
+!/src/extensions/dev/README.*
 
 /src/extensions/disabled
 

src/extensions/default/README.md

@@ -0,0 +1,6 @@
+# Brackets Default Extensions
+
+This directory contains extensions that ship with <strong>Brackets</strong> and are enabled
+by default. Examples include extensions for QuickOpen.
+
+(<code>README.md</code> serves as a dummy file so this directory can be added to git.)

src/extensions/dev/README.md

@@ -0,0 +1,8 @@
+# Brackets Dev Extensions
+
+This directory contains extensions that are being developed. User-installed
+extensions are placed in the "user" extensions directory, which can be accessed
+by running the <code>Help > Show Extensions Folder</code> menu command. The contents of
+this directory (except the <code>README.md</code> file) are ignored by git.
+
+(<code>README.md</code> also serves as a dummy file so this directory can be added to git.)

src/extensions/samples/README.txt → src/extensions/samples/README.md

@@ -1,5 +1,7 @@
-This directory contains extensions that should be disabled by default, but 
+# Brackets Example Extensions
+
+This directory contains extensions that should be disabled by default, but
 that we want to add to the repo. This might include things like examples and
 test cases.
 
-(README also serves as a dummy file so this directory can be added to git.)
+(<code>README.md</code> also serves as a dummy file so this directory can be added to git.)