added an .assert pragma and mentioned the pragmas in the changelog

compiler/pragmas.nim

@@ -1176,7 +1176,7 @@ proc singlePragma(c: PContext, sym: PSym, n: PNode, i: var int,
         if sym == nil: invalidPragma(c, it)
         else: sym.flags.incl sfUsed
       of wLiftLocals: discard
-      of wRequires, wInvariant, wAssume:
+      of wRequires, wInvariant, wAssume, wAssert:
         pragmaProposition(c, it)
       of wEnsures:
         pragmaEnsures(c, it)

compiler/sempass2.nim

@@ -1030,7 +1030,7 @@ proc track(tracked: PEffects, n: PNode) =
       when defined(drnim):
         if pragma == wAssume:
           addFact(tracked.guards, pragmaList[i][1])
-        elif pragma == wInvariant:
+        elif pragma == wInvariant or pragma == wAssert:
           if prove(tracked, pragmaList[i][1]):
             addFact(tracked.guards, pragmaList[i][1])
 

compiler/wordrecg.nim

@@ -54,7 +54,7 @@ type
     wNonReloadable, wExecuteOnReload,
     wAssertions, wPatterns, wTrMacros, wSinkInference, wWarnings,
     wHints, wOptimization, wRaises, wWrites, wReads, wSize, wEffects, wTags,
-    wRequires, wEnsures, wInvariant, wAssume,
+    wRequires, wEnsures, wInvariant, wAssume, wAssert,
     wDeadCodeElimUnused,  # deprecated, dead code elim always happens
     wSafecode, wPackage, wNoForward, wReorder, wNoRewrite, wNoDestroy,
     wPragma,
@@ -143,7 +143,7 @@ const
 
     "assertions", "patterns", "trmacros", "sinkinference", "warnings", "hints",
     "optimization", "raises", "writes", "reads", "size", "effects", "tags",
-    "requires", "ensures", "invariant", "assume",
+    "requires", "ensures", "invariant", "assume", "assert",
     "deadcodeelim",  # deprecated, dead code elim always happens
     "safecode", "package", "noforward", "reorder", "norewrite", "nodestroy",
     "pragma",