fix: Allow bookmark region to be set to 1 Byte length (#1747)

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### Problem description
<!-- Describe the bug that you fixed/feature request that you
implemented, or link to an existing issue describing it -->
When entering for the end value the same value as the start it is not
recorgnized as valid region, because end must be strictly greater than
begin. Due to the +1 in the Region constructor this is not correct,
because the end is included in the range.

### Implementation description
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### Screenshots
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make before/after sceenshots -->
After:

![image](https://github.com/WerWolv/ImHex/assets/10099533/c45d2001-8790-430a-8f1a-4b65130f4d01)


### Additional things
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plugins/builtin/source/content/views/view_bookmarks.cpp

@@ -440,7 +440,7 @@ namespace hex::plugin::builtin {
 
                             ImGui::PopItemWidth();
 
-                            if (updated && end > begin) {
+                            if (updated && end >= begin) {
                                 region = Region(begin, end - begin + 1);
                                 EventHighlightingChanged::post();
                             }