feat(snip): add basic "physics" snippets

lua/typstar/snippets/math.lua

@@ -74,6 +74,7 @@ return {
     snip('mt', '|->> ', {}, math),
     snip('cp', 'compose ', {}, math),
     snip('iso', 'tilde.equiv ', {}, math),
+    snip('nab', 'nabla ', {}, math),
     snip('cc', 'cases(\n\t<>\n)\\', { i(1, '1') }, math),
     snip('([A-Za-z])o([A-Za-z0-9]) ', '<>(<>) ', { cap(1), cap(2) }, math, 100, {
         maxTrigLength = 4,

lua/typstar/snippets/visual.lua

@@ -37,9 +37,11 @@ local operations = { -- first boolean: existing brackets should be kept; second
     { 'ht', 'hat', '', true, true },
     { 'br', 'macron', '', true, true },
     { 'dt', 'dot', '', true, true },
+    { 'dia', 'diaer', '', true, true },
     { 'ci', 'circle', '', true, true },
     { 'td', 'tilde', '', true, true },
     { 'nr', 'norm', '', true, true },
+    { 'arr', 'arrow', '', true, true },
     { 'vv', 'vec', '', true, true },
     { 'rt', 'sqrt', '', true, true },
     { 'flo', 'floor', '', true, true },