manuals: replace hyphens with em dashes

Fix some hyphens being improperly used as em dashes.
See https://www.grammarly.com/blog/hyphens-and-dashes/

Using em dashes may also allow Sphinx to hyphenate
and break lines in the best way.

Note that the first character after an em dash not
supposed to be capitalized, unless a specific
rule applies, typically when what follows is a proper noun.

Fix a few misuses of parentheses in following text.

(From yocto-docs rev: 5918f019f63f6e820b1168f4cc001faa1d1cdc6f)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/documentation/transitioning-to-a-custom-environment.rst b/documentation/transitioning-to-a-custom-environment.rst
index 6b34fedc26..ee1fc891ab 100644
--- a/documentation/transitioning-to-a-custom-environment.rst
+++ b/documentation/transitioning-to-a-custom-environment.rst
@@ -84,7 +84,7 @@ Transitioning to a custom environment for systems development
 
 #. **Now you're ready to create an image recipe**.
    There are a number of ways to do this. However, it is strongly recommended
-   that you have your own image recipe - don't try appending to existing image
+   that you have your own image recipe --- don't try appending to existing image
    recipes. Recipes for images are trivial to create and you usually want to
    fully customize their contents.