Markdown Lexer doesn't recognize strong/emph at the very beginning of the text #1492
Description
Reproduce:
from pygments.lexers.markup import MarkdownLexer
l = MarkdownLexer()
print(list(l.get_tokens("*bolded text*")))
# OUT: [(Token.Text, '*bolded'), (Token.Text, ' '), (Token.Text, 'text*'), (Token.Text, '\n')]
print(list(l.get_tokens(" *bolded text*")))
# OUT: [(Token.Text, ' '), (Token.Generic.Emph, '*bolded text*'), (Token.Text, '\n')]
print(list(l.get_tokens("**bolded text**")))
# OUT: [(Token.Text, '**bolded'), (Token.Text, ' '), (Token.Text, 'text**'), (Token.Text, '\n')]
print(list(l.get_tokens(" **bolded text**")))
# OUT: [(Token.Text, ' '), (Token.Generic.Strong, '**bolded text**'), (Token.Text, '\n')]As shown in the code, if I add a space before the bold-ed/emph-ed text, the lexer outputs Token.Generic.Strong for the entire bold-ed/emph-ed phrase.
If nothing precedes the bold-ed/emph-ed phrase, the lexer sees the phrase as regulart text and breaks down the phrase into parts.
Environment
Python: Python 3.8.3
Pygments: 2.6.1