Fix/be respectful of special characters like exclamation marks in highlight phrases since they are also word boundaries (#1890)

* Add missing includes

We would normally have these included in another file already, or even
the precompiled headers, but having the files included here too makes
testing single parts easier.

* Modify the regex building of highlight phrases for non-regex phrases

For phrases like !test, the word boundary checking we did before was not
enough, so we now check for either a word boundary, a whitespace
character, or the line start/end.

* Add tests for ensuring I haven't fully broken the highlight system

* Add changelog entry

src/controllers/highlights/HighlightPhrase.cpp

@@ -2,6 +2,13 @@
 
 namespace chatterino {
 
+namespace {
+
+    const QString REGEX_START_BOUNDARY("(\\b|\\s|^)");
+    const QString REGEX_END_BOUNDARY("(\\b|\\s|$)");
+
+}  // namespace
+
 QColor HighlightPhrase::FALLBACK_HIGHLIGHT_COLOR = QColor(127, 63, 73, 127);
 QColor HighlightPhrase::FALLBACK_REDEEMED_HIGHLIGHT_COLOR =
     QColor(28, 126, 141, 90);
@@ -27,8 +34,10 @@ HighlightPhrase::HighlightPhrase(const QString &pattern, bool hasAlert,
     , isRegex_(isRegex)
     , isCaseSensitive_(isCaseSensitive)
     , soundUrl_(soundUrl)
-    , regex_(isRegex_ ? pattern
-                      : "\\b" + QRegularExpression::escape(pattern) + "\\b",
+    , regex_(isRegex_
+                 ? pattern
+                 : REGEX_START_BOUNDARY + QRegularExpression::escape(pattern) +
+                       REGEX_END_BOUNDARY,
              QRegularExpression::UseUnicodePropertiesOption |
                  (isCaseSensitive_ ? QRegularExpression::NoPatternOption
                                    : QRegularExpression::CaseInsensitiveOption))
@@ -47,8 +56,10 @@ HighlightPhrase::HighlightPhrase(const QString &pattern, bool hasAlert,
     , isCaseSensitive_(isCaseSensitive)
     , soundUrl_(soundUrl)
     , color_(color)
-    , regex_(isRegex_ ? pattern
-                      : "\\b" + QRegularExpression::escape(pattern) + "\\b",
+    , regex_(isRegex_
+                 ? pattern
+                 : REGEX_START_BOUNDARY + QRegularExpression::escape(pattern) +
+                       REGEX_END_BOUNDARY,
              QRegularExpression::UseUnicodePropertiesOption |
                  (isCaseSensitive_ ? QRegularExpression::NoPatternOption
                                    : QRegularExpression::CaseInsensitiveOption))

src/controllers/highlights/HighlightPhrase.hpp

@@ -4,10 +4,14 @@
 #include "util/RapidJsonSerializeQString.hpp"
 #include "util/RapidjsonHelpers.hpp"
 
+#include <QColor>
 #include <QRegularExpression>
 #include <QString>
+#include <QUrl>
 #include <pajlada/serialize.hpp>
 
+#include <memory>
+
 namespace chatterino {
 
 class HighlightPhrase