prepare for 5.0.1

Update README and ReleaseNotes.

Also remove outdated workflow badge, add a couple new one, and hack around a
rendering issue where the last character of longer workflow names gets
overwritten by the status - which resulted in the arguably most important info
(which Qt version) being hidden.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

.github/workflows/linux-bionic-5.9.yml

@@ -1,4 +1,4 @@
-name: Ubuntu 18.04 / Qt 5.9
+name: Ubuntu 18.04 / Qt 5.9--
 on:
   push:
     branches:

.github/workflows/linux-focal-5.12.yml

@@ -1,4 +1,4 @@
-name: Ubuntu 20.04 / Qt 5.12
+name: Ubuntu 20.04 / Qt 5.12--
 on:
   push:
     branches:

.github/workflows/linux-groovy-5.14.yml

@@ -1,4 +1,4 @@
-name: Ubuntu 20.10 / Qt 5.14
+name: Ubuntu 20.10 / Qt 5.14--
 on:
   push:
     branches:

.github/workflows/linux-trusty-5.12.yml

@@ -1,4 +1,4 @@
-name: Ubuntu 14.04 / Qt 5.12 for AppImage
+name: Ubuntu 14.04 / Qt 5.12 for AppImage--
 on:
   push:
     branches:

.github/workflows/linux-tumbleweed-qt-latest.yml

@@ -1,4 +1,4 @@
-name: openSUSE/Tumbleweed / Qt latest
+name: openSUSE/Tumbleweed / Qt latest--
 on:
   push:
     branches: